Tag Archives: Geophysics

The Next Generation Arecibo Telescope: A preliminary study [IMA]

Posted on by

http://arxiv.org/abs/2305.07780


The Next Generation Arecibo Telescope (NGAT) was a concept presented in a white paper Roshi et al. (2021) developed by members of the Arecibo staff and user community immediately after the collapse of the 305 m legacy telescope. A phased array of small parabolic antennas placed on a tiltable plate-like structure forms the basis of the NGAT concept. The phased array would function both as a transmitter and as a receiver. This envisioned state of the art instrument would offer capabilities for three research fields, viz. radio astronomy, planetary and space & atmospheric sciences. The proposed structure could be a single plate or a set of closely spaced segments, and in either case it would have an equivalent collecting area of a parabolic dish of size 300 m. In this study we investigate the feasibility of realizing the structure. Our analysis shows that, although a single structure ~300 m in size is achievable, a scientifically competitive instrument 130 to 175 m in size can be developed in a more cost effective manner. We then present an antenna configuration consisting of one hundred and two 13 m diameter dishes. The diameter of an equivalent collecting area single dish would be ~130 m, and the size of the structure would be ~146 m. The weight of the structure is estimated to be 4300 tons which would be 53% of the weight of the Green Bank Telescope. We refer to this configuration as NGAT-130. We present the performance of the NGAT-130 and show that it surpasses all other radar and single dish facilities. Finally, we briefly discuss its competitiveness for radio astronomy, planetary and space & atmospheric science applications.

Read this paper on arXiv…

D. Roshi, S. Marshall, A. Vishwas, et. al.
Tue, 16 May 23
7/83

Comments: 6 pages, 5 figures, 1 table, Invited paper for the ICEAA-IEEE APWC conference, Venice, Italy, Oct 9-13, 2023

Effect of the inclination in the passage through the 5/3 mean motion resonance between Ariel and Umbriel [EPA]

Posted on by

http://arxiv.org/abs/2305.08794


The orbits of the main satellites of Uranus are expected to slowly drift away owing to tides raised in the planet. As a result, the 5/3 mean motion resonance between Ariel and Umbriel was likely encountered in the past. Previous studies have shown that, in order to prevent entrapment in this resonance, the eccentricities of the satellites must be larger than $\sim 0.01$ at the epoch, which is hard to explain. On the other hand, if the satellites experience some temporary capture and then escape, the inclinations rise to high values that are not observed today. We have revisited this problem both analytically and numerically focussing on the inclination, using a secular two-satellite model with circular orbits. We show that if the inclination of Umbriel was around $0.15^{\circ}$ at the time of the 5/3 resonance encounter, capture can be avoided in about $60\%$ of the cases. Moreover, after the resonance crossing, the inclination of Umbriel drops to a mean value around $0.08^{\circ}$, which is close to the presently observed one. The final inclination of Ariel is distributed between $0.01^{\circ}$ and $0.25^{\circ}$ with a nearly equal probability, which includes the present mean value of $0.02^{\circ}$.

Read this paper on arXiv…

S. Gomes and A. Correia
Tue, 16 May 23
76/83

Comments: 19 pages, 10 figures

Unsupervised noise reductions for gravitational reference sensors or accelerometers based on Noise2Noise method [CL]

Posted on by

http://arxiv.org/abs/2305.06735


Onboard electrostatic suspension inertial sensors are important applications for gravity satellites and space gravitational wave detection missions, and it is important to suppress noise in the measurement signal. Due to the complex coupling between the working space environment and the satellite platform, the process of noise generation is extremely complex, and traditional noise modeling and subtraction methods have certain limitations. With the development of deep learning, applying it to high-precision inertial sensors to improve the signal-to-noise ratio is a practically meaningful task. Since there is a single noise sample and unknown true value in the measured data in orbit, odd-even sub-samplers and periodic sub-samplers are designed to process general signals and periodic signals, and adds reconstruction layers consisting of fully connected layers to the model. Experimental analysis and comparison are conducted based on simulation data, GRACE-FO acceleration data and Taiji-1 acceleration data. The results show that the deep learning method is superior to traditional data smoothing processing sol

Read this paper on arXiv…

Z. Yang, H. Zhang, P. Xu, et. al.
Fri, 12 May 23
36/53

Comments: 16 pages, 17 figures

Discovery of a new lunar mineral rich in water and ammonium in lunar soils returned by Chang'e-5 mission [EPA]

Posted on by

http://arxiv.org/abs/2305.05263


The origin and distribution of lunar water are among the most important issues in understanding the earth-moon system. After more than half a century of laboratory research and remote detection, only hydroxyl contained minerals and lunar ice (H2O) are identified. Here we report the discovery of a hydrous mineral (NH4)MgCl3(H2O)6 in the lunar soil returned by Chang’e-5 mission, which contains 417,000 parts per million H2O. The determined structure and composition are similar to novograblenovite-a terrestrial fumarole mineral formed by reaction of hot basalt in water-rich volcanic gases, whereas the measured isotope composition delta37Cl reached 20.4 parts per thousand, a high value that only found in lunar minerals. We rule out the possibility that this hydrate originated from terrestrial contaminants or rocket exhaust through analysis of its chemical, isotopic compositions as well as the formation conditions. Our finding indicates that water can exist on some parts of the sunlit Moon in the form of hydrate compounds. Moreover, this hydrate is rich in ammonium, providing new information in understanding the origin of the Moon.

Read this paper on arXiv…

S. Jin, M. Hao, Z. Guo, et. al.
Wed, 10 May 23
11/65

Comments: 17 pages, 4 figures

Effect of Earth-Moon's gravity on TianQin's range acceleration noise. III. An analytical model [IMA]

Posted on by

http://arxiv.org/abs/2305.02539


TianQin is a proposed space-based gravitational wave detector designed to operate in circular high Earth orbits. As a sequel to [Zhang et al. Phys. Rev. D 103, 062001 (2021)], this work provides an analytical model to account for the perturbing effect of the Earth’s gravity field on the range acceleration noise between two TianQin satellites. For such an “orbital noise,” the Earth’s contribution dominates above $5\times 10^{-5}$ Hz in the frequency spectrum, and the noise calibration and mitigation, if needed, can benefit from in-depth noise modeling. Our model derivation is based on Kaula’s theory of satellite gravimetry with Fourier-style decomposition, and uses circular reference orbits as an approximation. To validate the model, we compare the analytical and numerical results in two main scenarios. First, in the case of the Earth’s static gravity field, both noise spectra are shown to agree well with each other at various orbital inclinations and radii, confirming our previous numerical work while providing more insight. Second, the model is extended to incorporate the Earth’s time-variable gravity. Particularly relevant to TianQin, we augment the formulas to capture the disturbance from the Earth’s free oscillations triggered by earthquakes, of which the mode frequencies enter TianQin’s measurement band above 0.1 mHz. The analytical model may find applications in gravity environment monitoring and noise-reduction pipelines for TianQin.

Read this paper on arXiv…

L. Jiao and X. Zhang
Fri, 5 May 23
19/67

Comments: 16 pages, 9 figures, accepted by Phys. Rev. D

First observations with a GNSS antenna to radio telescope interferometer [CL]

Posted on by

http://arxiv.org/abs/2304.11016


We describe the design of a radio interferometer composed of a Global Navigation Satellite Systems (GNSS) antenna and a Very Long Baseline Interferometry (VLBI) radio telescope. Our eventual goal is to use this interferometer for geodetic applications including local tie measurements. The GNSS element of the interferometer uses a unique software-defined receiving system and modified commercial geodetic-quality GNSS antenna. We ran three observing sessions in 2022 between a 25 m radio telescope in Fort Davis, Texas (FD-VLBA), a transportable GNSS antenna placed within 100 meters, and a GNSS antenna placed at a distance of about 9 km. We have detected a strong interferometric response with a Signal-to-Noise Ratio (SNR) of over 1000 from Global Positioning System (GPS) and Galileo satellites. We also observed natural radio sources including Galactic supernova remnants and Active Galactic Nuclei (AGN) located as far as one gigaparsec, thus extending the range of sources that can be referenced to a GNSS antenna by 18 orders of magnitude. These detections represent the first observations made with a GNSS antenna to radio telescope interferometer. We have developed a novel technique based on a Precise Point Positioning (PPP) solution of the recorded GNSS signal that allows us to extend integration time at 1.5 GHz to at least 20 minutes without any noticeable SNR degradation when a rubidium frequency standard is used.

Read this paper on arXiv…

J. Skeens, J. York, L. Petrov, et. al.
Mon, 24 Apr 23
23/41

Comments: 33 pages, 19 figures

Avoiding methane emission rate underestimates when using the divergence method [CL]

Posted on by

http://arxiv.org/abs/2304.10303


Methane is a powerful greenhouse gas, and a primary target for mitigating climate change in the short-term future due to its relatively short atmospheric lifetime and greater ability to trap heat in Earth’s atmosphere compared to carbon dioxide. Top-down observations of atmospheric methane are possible via drone and aircraft surveys as well as satellites such as the TROPOspheric Monitoring Instrument (TROPOMI). Recent work has begun to apply the divergence method to produce regional methane emission rate estimates. Here we show that spatially incomplete observations of methane can produce negatively biased time-averaged regional emission rate estimates via the divergence method, but that this effect can be counteracted by adopting a procedure in which daily advective fluxes of methane are time-averaged before the divergence method is applied. Using such a procedure with TROPOMI methane observations, we calculate yearly Permian emission rates of 3.1, 2.4 and 2.7 million tonnes per year for the years 2019 through 2021. We also show that highly-resolved plumes of methane can have negatively biased estimated emission rates by the divergence method due to the presence of turbulent diffusion in the plume, but this is unlikely to affect regional methane emission budgets constructed from TROPOMI observations of methane. The results from this work are expected to provide useful guidance for future implementations of the divergence method for emission rate estimation from satellite data – be it for methane or other gaseous species in the atmosphere.

Read this paper on arXiv…

C. Roberts, R. IJzermans, D. Randell, et. al.
Fri, 21 Apr 23
1/60

Comments: 17 pages, 10 figures, submitted to Environmental Research Letters

Earth shaped by primordial H$_2$ atmospheres [EPA]

Posted on by

http://arxiv.org/abs/2304.07845


Earth’s water, intrinsic oxidation state, and metal core density are fundamental chemical features of our planet. Studies of exoplanets provide a useful context for elucidating the source of these chemical traits. Planet formation and evolution models demonstrate that rocky exoplanets commonly formed with hydrogen-rich envelopes that were lost over time. These findings suggest that Earth may also have formed from bodies with H$_2$-rich primary atmospheres. Here we use a self-consistent thermodynamic model to show that Earth’s water, core density, and overall oxidation state can all be sourced to equilibrium between H$_2$-rich primary atmospheres and underlying magma oceans in its progenitor planetary embryos. Water is produced from dry starting materials resembling enstatite chondrites as oxygen from magma oceans reacts with hydrogen. Hydrogen derived from the atmosphere enters the magma ocean and eventually the metal core at equilibrium, causing metal density deficits matching that of Earth. Oxidation of the silicate rocks from solar-like to Earth-like oxygen fugacities also ensues as Si, along with H and O, alloys with Fe in the cores. Reaction with hydrogen atmospheres and metal-silicate equilibrium thus provides a simple explanation for fundamental features of Earth’s geochemistry that is consistent with rocky planet formation across the galaxy.

Read this paper on arXiv…

E. Young, A. Shahar and H. Schlichting
Tue, 18 Apr 23
32/80

Comments: 3 main figures, 5 auxiliary figures

How the Moon Impacts Subsea Communication Cables [CL]

Posted on by

http://arxiv.org/abs/2304.06905


We report tidal-induced latency variations on a transpacific subsea cable. Week-long recordings with a precision phase meter suggest length changes in the sub-meter range caused by the Poisson effect. The described method adds to the toolbox for the new field >>optical oceanic seismology<<.

Read this paper on arXiv…

L. Moeller
Mon, 17 Apr 23
2/51

Comments: N/A

Rapid solidification of Earth's magma ocean limits early lunar recession [EPA]

Posted on by

http://arxiv.org/abs/2304.04866


The early evolution of the Earth-Moon system prescribes the tidal environment of the Hadean Earth and holds the key to the formation mechanism of the Moon and its thermal evolution. Estimating its early state by backtracking from the present, however, suffers from substantial uncertainties associated with ocean tides. Tidal evolution during the solidification of Earth’s magma ocean, on the other hand, has the potential to provide robust constraints on the Earth-Moon system before the appearance of a water ocean. Here we show that energy dissipation in a solidifying magma ocean results in considerably more limited lunar recession than previously thought, and that the Moon was probably still at the distance of $\sim$7-9 Earth radii at the end of solidification. This limited early recession aggravates the often overlooked difficulty of modeling tidal dissipation in Earth’s first billion years, but it also offers a new possibility of resolving the lunar inclination problem by allowing the operation of multiple excitation mechanisms.

Read this paper on arXiv…

J. Korenaga
Wed, 12 Apr 23
33/45

Comments: N/A

Jupiter's cloud-level variability triggered by torsional oscillations in the interior [EPA]

Posted on by

http://arxiv.org/abs/2304.04460


Jupiter’s weather layer exhibits long-term and quasi-periodic cycles of meteorological activity that can completely change the appearance of its belts and zones. There are cycles with intervals from 4 to 9 years, dependent on the latitude, which were detected in 5$\mu$m radiation, which provides a window into the cloud-forming regions of the troposphere; however, the origin of these cycles has been a mystery. Here we propose that magnetic torsional oscillations/waves arising from the dynamo region could modulate the heat transport and hence be ultimately responsible for the variability of the tropospheric banding. These axisymmetric waves are magnetohydrodynamic waves influenced by the rapid rotation, which have been detected in Earth’s core, and have been recently suggested to exist in Jupiter by the observation of magnetic secular variations by Juno. Using the magnetic field model JRM33, together with the density distribution model, we compute the expected speed of these waves. For the waves excited by variations in the zonal jet flows, their wavelength can be estimated from the width of the alternating jets, yielding waves with a half period of 3.2-4.7 years in 14-23$^\circ$N, consistent with the intervals with the cycles of variability of Jupiter’s North Equatorial Belt and North Temperate Belt identified in the visible and infrared observations. The nature of these waves, including the wave speed and the wavelength, is revealed by a data-driven technique, dynamic mode decomposition, applied to the spatio-temporal data for 5$\mu$m emission. Our results imply that exploration of these magnetohydrodynamic waves may provide a new window to the origins of quasi-periodic patterns in Jupiter’s tropospheric clouds and to the internal dynamics and the dynamo of Jupiter.

Read this paper on arXiv…

K. Hori, C. Jones, A. Antuñano, et. al.
Tue, 11 Apr 23
50/63

Comments: N/A

A Data Science Approach to Study the Water Storage Capacity in Rocky Planet Mantles: Earth, Mars, and Exoplanets [CL]

Posted on by

http://arxiv.org/abs/2304.03700


Nominally anhydrous minerals (NAMs) are the primary carriers of water in rocky planet mantles. Therefore, studying water solubilities of major NAMs in the mantle can help us estimate the water storage capacities of rocky planet mantles and indirectly constrain the actual water contents of their interiors. By using data science methods such as statistics and statistical learning algorithms, in this paper, current modeling studies on the mantle water storage capacities of Earth, Mars, and exoplanets have been introduced and summarized. Firstly, the thermodynamic model for mantle water storage capacity has been reviewed. Then, based on the two case studies on Earth and Mars, how to translate atomic-scale experimental data of water solubility and their measurement errors into planetary-scale models of mantle water storage capacity has been explored by using robust regression, Monte Carlo methods, and bootstrap aggregation algorithms. Thirdly, how the large sample data from the exoplanet observational campaigns can help us understand the statistical properties of the mantle water storage capacities of rocky exoplanets has been introduced. Finally, the application limitations of data science methods in mineral physics research have been discussed, and how to better combine statistics and statistical algorithms with mineral physics data research has been prospected.

Read this paper on arXiv…

J. Dong
Mon, 10 Apr 23
35/36

Comments: 14 pages, 7 figures, a review article accepted by Bulletin of Mineralogy, Petrology and Geochemistry, in Chinese

Modeling meteorite craters by impacting melted tin on sand [EPA]

Posted on by

http://arxiv.org/abs/2303.18016


To simulate the heated exterior of a meteorite, we impact a granular bed with melted tin. The morphology of tin remnant and crater is found to be sensitive to the temperature and solidification of tin. By employing deep learning and convolutional neural network, we can quantify and map the complex impact patterns onto network systems based on feature maps and Grad-CAM results. This gives us unprecedented details on how the projectile deforms and interacts with the granules, which information can be used to trace the development of different remnant shapes. Furthermore, full dynamics of granular system is revealed by the use of Particle Image Velocimetry. Kinetic energy, temperature and diameter of the projectile are used to build phase diagrams for the morphology of both crater and tin remnant. In addition to successfully reproducing key features of simple and complex craters, we are able to detect a possible artifact when compiling crater data from field studies. The depth of craters from high-energy impacts in our work is found to be independent of their width. However, when mixing data from different energy, temperature and diameter of projectile, a bogus power-law relationship appears between them. Like other controlled laboratory researches, our conclusions have the potential to benefit the study of paint in industry and asteroid sampling missions on the surface of celestial bodies.

Read this paper on arXiv…

H. Huang, P. Tsai, C. Lu, et. al.
Mon, 3 Apr 23
44/53

Comments: 6 pages, 5 figures

The volcanic and radial expansion/contraction history of the Moon simulated by numerical models of magmatism in the convective mantle [EPA]

Posted on by

http://arxiv.org/abs/2303.16517


To understand the evolution of the Moon, we numerically modeled mantle convection and magmatism in a two-dimensional polar rectangular mantle. Magmatism occurs as an upward permeable flow of magma generated by decompression melting through the convecting matrix. The mantle is assumed to be initially enriched in heat-producing elements (HPEs) and compositionally dense ilmenite-bearing cumulates (IBC) at its base. Here, we newly show that magma generation and migration play a crucial role in the calculated volcanic and radial expansion/contraction history. Magma is generated in the deep mantle by internal heating for the first several hundred million years. A large volume of the generated magma ascends to the surface as partially molten fingers and plumes driven by melt-buoyancy to cause a volcanic activity and radial expansion of the planet with the peak at 3.5-4 Gyr ago. Eventually, however, the planet begins to radially contract when the mantle solidifies by cooling from the surface boundary. As the mantle is cooled, the activity of partially molten plumes declines but continues for billions of years after the peak because some basal materials enriched in the dense IBC components hold HPEs. The calculated volcanic and radial expansion/contraction history is consistent with the observed history of the Moon. Our simulations suggest a substantial fraction of the mantle was solid, and there was a basal layer enriched in HPEs and the IBC components at the beginning of the history of the Moon.

Read this paper on arXiv…

K. U, M. Kameyama and M. Ogawa
Thu, 30 Mar 23
48/66

Comments: 36 pages, 10 figures, and 3 tables

The radiation environment over the African continent at aviation altitudes: First results of the RPiRENA-based dosimeter [CL]

Posted on by

http://arxiv.org/abs/2303.15452


The radiation environment over the African continent, at aviation altitudes, remains mostly uncharacterized and unregulated. In this paper we present initial measurements made by a newly developed active dosimeter on-board long-haul flights between South Africa and Germany. Based on these initial tests, we believe that this low-cost and open-source dosimeter is suitable for continued operation over the Africa continent and can provide valuable long-term measurements to test dosimteric models and inform aviation policy

Read this paper on arXiv…

M. Mosotho, R. Strauss, S. S.Bottcher, et. al.
Wed, 29 Mar 23
68/73

Comments: Accepted to appear in Journal of Space Weather and Space Climate

Igneous Rim Accretion on Chondrules in Low-Velocity Shock Waves [EPA]

Posted on by

http://arxiv.org/abs/2303.10450


Shock wave heating is a leading candidate for the mechanisms of chondrule formation. This mechanism forms chondrules when the shock velocity is in a certain range. If the shock velocity is lower than this range, dust particles smaller than chondrule precursors melt, while chondrule precursors do not. We focus on the low-velocity shock waves as the igneous rim accretion events. Using a semi-analytical treatment of the shock-wave heating model, we found that the accretion of molten dust particles occurs when they are supercooling. The accreted igneous rims have two layers, which are the layers of the accreted supercooled droplets and crystallized dust particles. We suggest that chondrules experience multiple rim-forming shock events.

Read this paper on arXiv…

Y. Matsumoto and S. Arakawa
Tue, 21 Mar 23
66/68

Comments: accepted for publication in ApJ

M$^5$ — Mars Magnetospheric Multipoint Measurement Mission: A multi-spacecraft plasma physics mission to Mars [CL]

Posted on by

http://arxiv.org/abs/2303.09502


Mars, lacking an intrinsic dynamo, is an ideal laboratory to comparatively study induced magnetospheres, which can be found in other terrestrial bodies as well as comets. Additionally, Mars is of particular interest to further exploration due to its loss of habitability by atmospheric escape and possible future human exploration. In this context, we propose the Mars Magnetospheric Multipoint Measurement Mission (M$^5$), a multi-spacecraft mission to study the dynamics and energy transport of the Martian induced magnetosphere comprehensively. Particular focus is dedicated to the largely unexplored magnetotail region, where signatures of magnetic reconnection have been found. Furthermore, a reliable knowledge of the upstream solar wind conditions is needed to study the dynamics of the Martian magnetosphere, especially the different dayside boundary regions but also for energy transport phenomena like the current system and plasma waves. This will aid the study of atmospheric escape processes of planets with induced magnetospheres. In order to resolve the three-dimensional structures varying both in time and space, multi-point measurements are required. Thus, M$^5$ is a five spacecraft mission, with one solar wind monitor orbiting Mars in a circular orbit at 5 Martian radii, and four smaller spacecraft in a tetrahedral configuration orbiting Mars in an elliptical orbit, spanning the far magnetotail up to 6 Mars radii with a periapsis within the Martian magnetosphere of 1.8 Mars radii. We not only present a detailed assessment of the scientific need for such a mission but also show the resulting mission and spacecraft design taking into account all aspects of the mission requirements and constraints such as mass, power, and link budgets. This mission concept was developed during the Alpbach Summer School 2022.

Read this paper on arXiv…

C. Larkin, V. Lundén, L. Schulz, et. al.
Fri, 17 Mar 23
44/67

Comments: 16 pages, 9 figures. Submitted to Advances in Space Research

Tracing the history of an unusual compound presolar grain from progenitor star to asteroid parent body host [EPA]

Posted on by

http://arxiv.org/abs/2301.08228


We conducted a TEM study of an unusual oxide-silicate composite presolar grain (F2-8) from the unequilibrated ordinary chondrite Semarkona. The presolar composite grain is relatively large, has an amoeboidal shape, and contains Mg-rich olivine, Mg-Al spinel, and Ca-rich pyroxene. The shape and phase assemblage are reminiscent of amoeboid-olivine-aggregates and add to the growing number of TEM observations of presolar refractory inclusion-like (CAIs and AOAs) grains. In addition to the dominant components, F2-8 also contains multiple subgrains, including an alabandite-oldhamite composite grain within the olivine and several magnetite subgrains within the Mg-Al spinel. We argue that the olivine, Mg-Al spinel, and alabandite-oldhamite formed by equilibrium condensation, whereas the Ca-rich pyroxene formed by non-equilibrium condensation, all in an M-type AGB star envelope. On the other hand, the magnetite subgrains are likely the result of aqueous alteration on the Semarkona asteroidal parent body. Additional evidence of secondary processing includes Fe-enrichment in the Mg-Al spinel and olivine, elevated Al contents in the olivine, and beam sensitivity and a modulated structure for the olivine. Compound presolar grains record condensation conditions over a wide range of temperatures. Additionally, the presence of several different presolar phases in a composite grain can impart information on the relative rates and effects of post-condensation processing in a range of environments, including the interstellar medium, solar nebula, and the host asteroid parent body. The TEM observations of F2-8 provide insights across the lifetime of the grain from its formation by condensation in an M-type AGB star envelope, its transit through the interstellar medium, and aqueous alteration during its residence on Semarkona’s asteroidal parent body.

Read this paper on arXiv…

S. Singerling, L. Nittler, J. Barosch, et. al.
Fri, 20 Jan 23
6/72

Comments: 36 total pages, including 6 figures, 3 supplemental figures, 4 tables, and 2 supplemental tables

On computing viscoelastic Love numbers for general planetary models: the \texttt{ALMA${}^3$} code [EPA]

Posted on by

http://arxiv.org/abs/2301.07351


The computation of the Love numbers for a spherically symmetric self-gravitating viscoelastic Earth is a classical problem in global geodynamics. Here we revisit the problem of the numerical evaluation of loading and tidal Love numbers in the static limit for an incompressible planetary body, adopting a Laplace inversion scheme based upon the Post-Widder formula as an alternative to the {traditional viscoelastic normal modes method. We also consider, whithin the same framework, complex-valued, frequency-dependent Love numbers that describe the response to a periodic forcing, which are paramount in the study of the tidal deformation of planets. Furthermore, we numerically obtain the time-derivatives of Love numbers, suitable for modeling geodetic signals in response to surface loads variations. A number of examples are shown, in which time and frequency-dependent Love numbers are evaluated for the Earth and planets adopting realistic rheological profiles. The numerical solution scheme is implemented in ALMA${}^3$ (the plAnetary Love nuMbers cAlculator, version 3), an upgraded open-source Fortran 90 program that computes the Love numbers for radially layered planetary bodies with a wide range of rheologies, including transient laws like Andrade or Burgers.

Read this paper on arXiv…

D. Melini, C. Saliby and G. Spada
Thu, 19 Jan 23
30/100

Comments: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Geophysical Journal International following peer review. The version of record is available online at this https URL

Glycine amino acid transformation under impacts by small solar system bodies, simulated via high-pressure torsion method [EPA]

Posted on by

http://arxiv.org/abs/2301.06927


Impacts by small solar system bodies (meteoroids, asteroids, comets and transitional objects) are characterized by a combination of energy dynamics and chemical modification on both terrestrial and small solar system bodies. In this context, the discovery of glycine amino acid in meteorites and comets has led to a hypothesis that impacts by astronomical bodies could contribute to delivery and polymerization of amino acids in the early Earth to generate proteins as essential molecules for life. Besides the possibility of abiotic polymerization of glycine, its decomposition by impacts could generate reactive groups to form other essential organic biomolecules. In this study, the high-pressure torsion (HPT) method, as a new platform for simulation of impacts by small solar system bodies, was applied to glycine. In comparison with high-pressure shock experiments, the HPT method simultaneously introduces high pressure and deformation strain. It was found that glycine was not polymerized in the experimental condition assayed, but partially decomposed to ethanol under pressures of 1 and 6 GPa and shear strains of <120 m/m. The detection of ethanol implies the inherent availability of remaining nitrogen-containing groups, which can incorporate to the formation of other organic molecules at the impact site. In addition, this finding highlights a possibility of the origin of ethanol previously detected in comets.

Read this paper on arXiv…

K. Edalati, I. Taniguchi, R. Floriano, et. al.
Wed, 18 Jan 23
58/133

Comments: N/A

Chelyabinsk : a rock with many different (stony) faces: An infrared study [EPA]

Posted on by

http://arxiv.org/abs/2301.06525


In order to provide spectral ground truth data for remote sensing applications, we have measured midinfrared spectra (2 to 18 micron) of three typical, well defined lithologies from the Chelyabinsk meteorite. These lithologies are classified as (a) moderately shocked, light lithology, (b) shock darkened lithology, and (c) impact melt lithology. Analyses were made from bulk material in four size fractions (0 to 25 micron, 25 to 63 micron, 63 to 125 micron, and 125 to 250 micron), and from additional thin sections. Characteristic infrared features in the powdered bulk material of the moderately shocked, light lithology, dominated by olivine, pyroxene and feldspathic glass, are a Christiansen feature (CF) between 8.5 and 8.8 micron; a transparency feature (TF) in the finest size fraction at about 13 micron, and strong reststrahlen bands (RB) at about 9.1 micron, 9.5 micron, 10.3 micron, 10.8 micron, 11.2 to 11.3 micron, 12 micron, and between 16 and 17 micron. The ranges of spectral features for the micro FTIR spots show a wider range than those obtained in diffuse reflectance, but are generally similar. With increasing influence of impact shock from pristine LL5 (or LL6) material (which have a low or moderate degree of shock) to the shock-darkened lithology and the impact melt lithology as endmembers, we observe the fading or disappearing of spectral features. Most prominent is the loss of a twin peak feature between 10.8 and 11.3 micron, which turns into a single peak. In addition, in the pure impact melt endmember lithology features at about 9.6 micron and about 9.1 micron are also lost. These losses are most likely correlated with decreasing amounts of crystal structure as the degree of shock melting increases.

Read this paper on arXiv…

A. Morlok, A. Bischoff, M. Patzeck, et. al.
Wed, 18 Jan 23
92/133

Comments: N/A

Science Priorities for the Extraction of the Solid MSR Samples from their Sample Tubes [IMA]

Posted on by

http://arxiv.org/abs/2301.04694


Preservation of the chemical and structural integrity of samples that will be brought back from Mars is paramount to achieving the scientific objectives of MSR. Given our knowledge of the nature of the samples retrieved at Jezero by Perseverance, at least two options need to be tested for opening the sample tubes: (1) One or two radial cuts at the end of the tube to slide the sample out. (2) Two radial cuts at the ends of the tube and two longitudinal cuts to lift the upper half of the tube and access the sample. Strategy 1 will likely minimize contamination but incurs the risk of affecting the physical integrity of weakly consolidated samples. Strategy 2 will be optimal for preserving the physical integrity of the samples but increases the risk of contamination and mishandling of the sample as more manipulations and additional equipment will be needed. A flexible approach to opening the sample tubes is therefore required, and several options need to be available, depending on the nature of the rock samples returned. Both opening strategies 1 and 2 may need to be available when the samples are returned to handle different sample types (e.g., loosely bound sediments vs. indurated magmatic rocks). This question should be revisited after engineering tests are performed on analogue samples. The MSR sample tubes will have to be opened under stringent BSL4 conditions and this aspect needs to be integrated into the planning.

Read this paper on arXiv…

N. Dauphas, S. Russell, D. Beaty, et. al.
Fri, 13 Jan 23
50/72

Comments: 8 pages, 3 figures, 1 table, report NASA-ESA Mars Rock Team Report

Mid-infrared bi-directional reflectance spectroscopy of impact melt glasses and tektites [EPA]

Posted on by

http://arxiv.org/abs/2301.04476


We have analyzed 14 impact melt glass samples, covering the compositional range from highly felsic to mafic/basaltic, as part of our effort to provide mid-infrared spectra (7-14 micron) for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer), an instrument onboard of the ESA/JAXA BepiColombo mission.
Since Mercury was exposed to many impacts in its history, and impact glasses are also common on other bodies, powders of tektites (Irghizite, Libyan Desert Glass, Moldavite, Muong Nong, Thailandite) and impact glasses (from the Dellen, El’gygytgyn, Lonar, Mien, Mistastin, and Popigai impact structures) were analyzed in four size fractions of (0-25, 25-63, 93-125 and 125-250 micron) from 2.5 to 19 micron in bi-directional reflectance. The characteristic Christiansen Feature (CF) is identified between 7.3 micron (Libyan Desert Glass) and 8.2 micron (Dellen). Most samples show mid-infrared spectra typical of highly amorphous material, dominated by a strong Reststrahlen Band (RB) between 8.9 micron (Libyan Desert Glass) and 10.3 micron (Dellen). Even substantial amounts of mineral fragments hardly affect this general band shape. Comparisons of the SiO2 content representing the felsic/mafic composition of the samples with the CF shows felsic/intermediate glass and tektites forming a big group, and comparatively mafic samples a second one. An additional sign of a highly amorphous state is the lack of features at wavelengths longer than about 15 micron. The tektites and two impact glasses, Irghizite and El’gygytgyn respectively, have much weaker water features than most of the other impact glasses.

Read this paper on arXiv…

A. Morlok, A. Stojic, I. Weber, et. al.
Thu, 12 Jan 23
57/68

Comments: N/A

Meteorite Parent Body Aqueous Alteration Simulations of Interstellar Residue Analogs [EPA]

Posted on by

http://arxiv.org/abs/2301.04103


Some families of carbonaceous chondrites are rich in prebiotic organics that may have contributed to the origin of life on Earth and elsewhere. However, the formation and chemical evolution of complex soluble organic molecules from interstellar precursors under relevant parent body conditions has not been thoroughly investigated. In this study, we approach this topic by simulating meteorite parent body aqueous alteration of interstellar residue analogs. The distributions of amines and amino acids are qualitatively and quantitatively investigated and linked to closing the gap between interstellar and meteoritic prebiotic organic abundances. We find that the abundance trend of methylamine > ethylamine> glycine > serine > alanine > \b{eta}-alanine does not change from pre- to post-aqueous alteration, suggesting that certain cloud conditions have an influential role on the distributions of interstellar-inherited meteoritic organics. However, the abundances for most of the amines and amino acids studied here varied by about 2-fold when aqueously processed for 7 days at 125 {\deg}C, and the changes in the {\alpha}- to \b{eta}-alanine ratio were consistent with those of aqueously altered carbonaceous chondrites, pointing to an influential role of meteorite parent body processing on the distributions of interstellar-inherited meteoritic organics. We detected higher abundances of {\alpha}- over \b{eta}-alanine, which is opposite to what is typically observed in aqueously altered carbonaceous chondrites; these results may be explained by at least the lack of minerals and insoluble organic matter-relevant materials in the experiments. The high abundance of volatile amines in the non-aqueously altered samples suggests that these types of interstellar volatiles can be efficiently transferred to asteroids and comets, supporting the idea of the presence of interstellar organics in solar system objects.

Read this paper on arXiv…

D. Qasim, H. McLain, J. Aponte, et. al.
Wed, 11 Jan 23
11/80

Comments: Published in ACS Earth and Space Chemistry; Supporting Info available at this https URL

Earth as a time crystal: macroscopic nature of a quantum-scale phenomenon from transformative moderation of geomagnetic polarity, topography, and climate by precession resonance due to many-body entrainment [CL]

Posted on by

http://arxiv.org/abs/2301.02578


Claims of paleodata periodicity are many and so controversial that superimposing Phanerozoic (0-541 My) mass-extinction periods renders life on Earth impossible. This period hunt coincided with geochronology modernization tying geological timescales to orbital frequencies, enabling separation of astronomical signals from harmonics. I thus show on diverse data (geomagnetic polarity, cratering, extinction episodes) as a proxy of planetary paleodynamics that many-body subharmonic entrainment induces Earth’s resonant response to astronomical forcing so that $2\pi$-phase-shifted axial precession p=26 ky and its Pi=$2\pi$p/i; i=1,…n harmonics get resonantly responsible for paleodata periodicity. This quasiperiodic nature of strata is co-triggered by a p’/4-lockstep to p’=41-ky obliquity. For verification, residuals analysis after suppressing $2\pi$p (and so Pi) in GPTS-95 reversals timescale’s calibration at the South Atlantic Anomaly, extending to end-Campanian (0-83 My), successfully detected weak signals of Earth-Mars planetary resonances reported previously from older epochs. The only residual signal is 26.5-My Rampino period — carrier wave of crushing deflections and transformative polarity reversals. While the ($2\pi$p, Pi) resonant response of the Earth to orbital forcing is the long-sought energy transfer mechanism of the Milankovitch theory, fundamental system properties — $2\pi$-phase-shift, 1/4 lockstep to a forcer, and discrete time translation symmetry (multiplied/halved periods) — typical of a quantum time crystal, here appear macroscopic, making time crystal concept unremarkable. The surprising cross-scale outcome confirms planetary precession is a cataclysmic geodynamic phenomenon as claimed previously, e.g., as the Earth expansion mechanism; then a time crystal in quantum dynamics could be due to particle entrainment, such as the collisions resulting in Feshbach resonances.

Read this paper on arXiv…

M. Omerbashich
Mon, 9 Jan 23
38/59

Comments: N/A

Enabling Ice Core Science on Mars and Ocean Worlds [CL]

Posted on by

http://arxiv.org/abs/2301.01869


Ice deposits on Earth provide an extended record of volcanism, planetary climate, and life. On Mars, such a record may extend as far back as tens to hundreds of millions of years (My), compared to only a few My on Earth. Here, we propose and demonstrate a compact instrument, the Melter-Sublimator for Ice Science (MSIS), and describe its potential use cases. Similar to current use in the analysis of ice cores, linking MSIS to downstream elemental, chemical, and biological analyses could address whether Mars is, or was in the recent past, volcanically active, enable the creation of a detailed climate history of the late Amazonian, and seek evidence of subsurface life preserved in ice sheets. The sublimation feature can not only serve as a preconcentrator for in-situ analyses, but also enable the collection of rare material such as cosmogenic nuclides, which could be returned to Earth and used to confirm and expand the record of nearby supernovas and long-term trends in space weather. Missions to Ocean Worlds such as Europa or Enceladus will involve ice processing, and there MSIS would deliver liquid samples for downstream wet chemistry analyses. Our combined melter-sublimator system can thus help to address diverse questions in heliophysics, habitability, and astrobiology.

Read this paper on arXiv…

A. Chipps, C. Tunis, N. Chellman, et. al.
Fri, 6 Jan 23
17/55

Comments: 10 pages, 5 figures

Mid-Infrared spectroscopy of impactites from the Noerdlinger Ries impact crater [EPA]

Posted on by

http://arxiv.org/abs/2301.01683


This study is part of an effort to build a mid-infrared database (7-14micron) of spectra for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer), an instrument onboard of the ESA/JAXA BepiColombo space probe to be launched to Mercury in 2017. Mercury was exposed to abundant impacts throughout its history. This study of terrestrial impactites can provide estimates of the effects of shock metamorphism on the mid-infrared spectral properties of planetary materials. In this study, we focus on the Noerdlinger Ries crater in Southern Germany, a well preserved and easily accessible impact crater with abundant suevite impactites. Suevite and melt glass bulk samples from Otting and Aumuehle, as well as red suevite from Polsingen were characterized and their reflectance spectra in mid-infrared range obtained. In addition, in-situ mid-infrared spectra were made from glasses and matrix areas in thin sections. The results show similar, but distinguishable spectra for both bulk suevite and melt glass samples, as well as in-situ measurements. Impact melt glass from Aumuehle and Otting have spectra dominated by a Reststrahlen band at 9.3-9.6 micron. Bulk melt rock from Polsingen and bulk suevite and fine-grained matrix have their strongest band between 9.4 to 9.6 micron. There are also features between 8.5 and 9 micron, and 12.5 – 12.8 micron associated with crystalline phases. There is evidence of weathering products in the fine-grained matrix, such as smectites. Mercury endured many impacts with impactors of all sizes over its history. So spectral characteristics observed for impactites formed only in a single impact like in the Ries impact event can be expected to be very common on planetary bodies exposed to many more impacts in their past. We conclude that in mid-infrared remote sensing data the surface of Mercury can be expected to be dominated by features of amorphous materials.

Read this paper on arXiv…

A. Morlok, A. Stojic, I. Dittmar, et. al.
Thu, 5 Jan 23
36/51

Comments: N/A

Gaia search for early-formed andesitic asteroidal crusts [EPA]

Posted on by

http://arxiv.org/abs/2301.00699


Context. Andesitic meteorites are among the oldest achondrites known to date. They record volcanic events and crust formation episodes in primordial planetesimals that took place about 4.565 Myr ago. However, no analogue for these meteorites has been found in the asteroid population to date. Aims. We searched for spectroscopic analogues of the andesitic meteorite Erg Chech 002 in the asteroid population using the Gaia DR3 spectral dataset. Methods. In order to identify which asteroids have the most similar spectrum to Erg Chech 002, we first determined the spectral parameters of Gaia DR3 asteroids (spectral slope and Band I depth) and compared them to the spectral parameters of different samples of the meteorite. In addition, we performed a spectral curve matching between Erg Chech 002 and Gaia DR3 asteroid data, and we compared the results of both methods. Results. We found that 51 main-belt asteroids have a visible spectrum similar to the one of Erg Chech 002, and 91 have a spectrum similar to the space-weathered spectra of the meteorite, corresponding to 0.08 and 0.15% of the whole Gaia DR3 dataset of asteroids with spectra, respectively. The asteroids that best match the laboratory samples of the meteorite are mostly located in the inner main belt, while the objects matching the space-weathered meteorite models show slightly more scattering across the belt. Conclusions. Despite the fact that we find asteroids that potentially match Erg Chech 002, these asteroids are extremely rare. Moreover, a visible spectrum alone is not completely diagnostic of an Erg Chech 002-like composition. Near-infrared spectra will be important to confirm (or rule out) the spectral matches between Erg Chech 002 and the candidate asteroid population.

Read this paper on arXiv…

M. Galinier, M. Delbo, C. Avdellidou, et. al.
Tue, 3 Jan 23
7/49

Comments: N/A

Simple physics and integrators accurately reproduce Mercury instability statistics [EPA]

Posted on by

http://arxiv.org/abs/2212.14844


The long-term stability of the Solar System is an issue of significant scientific and philosophical interest. The mechanism most likely to lead to instability is Mercury’s eccentricity being pumped up to a high enough value that Mercury is either scattered by or collides with Venus. Previously, only three five-billion-year $N$-body ensembles of the Solar System with thousands of simulations have been run to assess long-term stability. We generate two additional ensembles, each with 2750 members, and make them publicly available at https://archive.org/details/@dorianabbot. We find that accurate Mercury instability statistics can be obtained by (1) including only the Sun and the 8 planets, (2) using a simple Wisdom-Holman scheme without correctors, (3) using a basic representation of general relativity, and (4) using a time step of 3.16 days. By combining our Solar System ensembles with previous ensembles we form a 9,601-member ensemble of ensembles. In this ensemble of ensembles, the logarithm of the frequency of a Mercury instability event increases linearly with time between 1.3 and 5 Gyr, suggesting that a single mechanism is responsible for Mercury instabilities in this time range and that this mechanism becomes more active as time progresses. Our work provides a robust estimate of Mercury instability statistics over the next five billion years, outlines methodologies that may be useful for exoplanet system investigations, and provides two large ensembles of publicly available Solar System integrations that can serve as testbeds for theoretical ideas as well as training sets for artificial intelligence schemes.

Read this paper on arXiv…

D. Abbot, D. Hernandez, S. Hadden, et. al.
Mon, 2 Jan 23
26/44

Comments: submitted to ApJ

Mid-infrared spectra of differentiated meteorites (achondrites): Comparison with astronomical observations of dust in protoplanetary and debris disks [EPA]

Posted on by

http://arxiv.org/abs/2212.13959


Mid-infrared (5 micron to 25 micron) transmission/absorption spectra of differentiated meteorites (achondrites) were measured to permit comparison with astronomical observations of dust in different stages of evolution of young stellar objects. In contrast to primitive chondrites, achondrites underwent heavy metamorphism and/or extensive melting and represent more advanced stages of planetesimal evolution. Spectra were obtained from primitive achondrites (acapulcoite, winonaite, ureilite, and brachinite) and differentiated achondrites (eucrite, diogenite, aubrite, and mesosiderite silicates). The ureilite and brachinite show spectra dominated by olivine features, and the diogenite and aubrite by pyroxene features. The acapulcoite, winonaite, eucrite, and mesosiderite silicates exhibit more complex spectra, reflecting their multi-phase bulk mineralogy. Mixtures of spectra of the primitive achondrites and differentiated achondrites in various proportions show good similarities to the spectra of the few Myr old protoplanetary disks HD104237A and V410 Anon 13. A spectrum of the differentiated mesosiderite silicates is similar to the spectra of the mature debris disks HD172555 and HD165014. A mixture of spectra of the primitive ureilite and brachinite is similar to the spectrum of the debris disk HD113766. The results raise the possibility that materials produced in the early stage of planetesimal differentiation occur in the protoplanetary and debris disks.

Read this paper on arXiv…

A. Morlok, C. Koike, K. Tomeoka, et. al.
Thu, 29 Dec 22
7/47

Comments: N/A

Non-Ellipsoidal Gravity-Based Definitions of Planetary Surface Area and Other Geodetic Measures [EPA]

Posted on by

http://arxiv.org/abs/2212.12580


This paper introduces new definitions of common geodetic measures on a planetary surface (namely surface area, path length, and mean value or other statistical parameters of a surface function) that are not based on a datum such as a reference ellipsoid. Instead, the so-called datumless geodetic measures are based on physically meaningful formulations that rely only on the actual planetary surface and gravity. The datumless measures provide universally standardized measurements on any terrestrial object, including non-ellipsoidal asteroids and comets. Conveniently, on fairly round planets such as Earth and Mars, the datumless measures yield very similar values as corresponding geodetic measures on a reference ellipsoid. Like their ellipsoidal counterparts, the datumless measures quantify area and length in the familiar “bird’s-eye view” or “horizontal, normal-to-gravity” sense. Far from being purely theoretical, the datumless measures can be approximated in GIS software using a digital elevation model and a gravity model such as a geoid.

Read this paper on arXiv…

K. Xu
Tue, 27 Dec 22
8/30

Comments: 9 pages, 5 figures, 1 table

Non-Ellipsoidal Gravity-Based Definitions of Planetary Surface Area and Other Geodetic Measures [EPA]

Posted on by

http://arxiv.org/abs/2212.12580


This paper introduces new definitions of common geodetic measures on a planetary surface (namely surface area, path length, and mean value or other statistical parameters of a surface function) that are not based on a datum such as a reference ellipsoid. Instead, the so-called datumless geodetic measures are based on physically meaningful formulations that rely only on the actual planetary surface and gravity. The datumless measures provide universally standardized measurements on any terrestrial object, including non-ellipsoidal asteroids and comets. Conveniently, on fairly round planets such as Earth and Mars, the datumless measures yield very similar values as corresponding geodetic measures on a reference ellipsoid. Like their ellipsoidal counterparts, the datumless measures quantify area and length in the familiar “bird’s-eye view” or “horizontal, normal-to-gravity” sense. Far from being purely theoretical, the datumless measures can be approximated in GIS software using a digital elevation model and a gravity model such as a geoid.

Read this paper on arXiv…

K. Xu
Tue, 27 Dec 22
25/30

Comments: 9 pages, 5 figures, 1 table

Space Weather: From Solar Origins to Risks and Hazards Evolving in Time [CL]

Posted on by

http://arxiv.org/abs/2212.11504


Space Weather is the portion of space physics that has a direct effect on humankind. Space Weather is an old branch of space physics that originates back to 1808 with the publication of a paper by the great naturalist Alexander von Humboldt (von Humboldt, 1808). Space Weather is currently experiencing explosive growth, because its effects on human technologies have become more and more diverse. Space Weather is due to the variability of solar processes that cause interplanetary, magnetospheric, ionospheric, atmospheric and ground level effects. Space Weather can at times have strong impacts on technological systems and human health. The threats and risks are not hypothetical, and in the event of extreme Space Weather events the consequences could be quite severe for humankind. The purpose of the review is to give a brief overall view of the full chain of physical processes responsible for Space Weather risks and hazards, tracing them from solar origins to effects and impacts in interplanetary space, in the Earth’s magnetosphere and ionosphere and at the ground. The paper shows that the risks associated with Space Weather have not been constant over time; they have evolved as our society becomes more and more technologically advanced. The paper begins with a brief introduction to the Carrington event. Next, the descriptions of the strongest known Space Weather processes are reviewed. The concepts of geomagnetic storms and substorms are briefly introduced. The main effects/impacts of Space Weather are also considered, including geomagnetically induced currents (GICs) which are thought to cause power outages. The effects of radiation on avionics and human health, ionospheric effects and impacts, and thermosphere effects and satellite drag will also be discussed. Finally, we will discuss the current challenges of Space Weather forecasting and examine some of the worst-case scenarios.

Read this paper on arXiv…

N. Buzulukova and B. Tsurutani
Fri, 23 Dec 22
12/58

Comments: Review article, 4 figures

Daily detection and quantification of methane leaks using Sentinel-3: a tiered satellite observation approach with Sentinel-2 and Sentinel-5p [CL]

Posted on by

http://arxiv.org/abs/2212.11318


The twin Sentinel-3 satellites have multi-band radiometers which observe at methane-sensitive shortwave infrared bands with daily global coverage and 500 m ground pixel resolution. We investigate the methane observation capability of Sentinel-3 and how its coverage-resolution combination fits between Sentinel-5p and Sentinel-2. We show that methane plume enhancements can be retrieved from the shortwave infrared bands of Sentinel-3. We report a lowest emission detection by Sentinel-3 of 9 t/h under favorable detection conditions of low wind speeds and high surface albedo. We demonstrate Sentinel-3-based identification and monitoring of methane leaks using two case studies. Near Moscow, Sentinel-3 shows that two major short-term leaks separated by 30 km occurred simultaneously at a gas pipeline and appear as a single methane plume in Sentinel-5p data. For a major Sentinel-5p leak detection near the Hassi Messaoud oil/gas field in Algeria, Sentinel-3 identifies the leaking facility emitting continuously for 6 days, and Sentinel-2 pinpoints the source of the leak at an oil/gas well. Sentinel-2 and Sentinel-3 also show the 6-day leak was followed by a four-month period of burning of the leaking gas, suggesting a gas well blowout to be the cause of the leak. We find similar source rate quantifications from plume detections by Sentinel-3 and Sentinel-2 for these leaks, demonstrating utility of Sentinel-3 for emission quantification. These case studies show that zooming in with Sentinel-3 and Sentinel-2 in synergy allows precise identification and quantification as well as monitoring of the sources corresponding to methane anomalies observed in global scans of Sentinel-5p.

Read this paper on arXiv…

S. Pandey, M. Nistelrooij, J. Maasakkers, et. al.
Fri, 23 Dec 22
25/58

Comments: N/A

Experimentally shock-induced melt veins in basalt: Improving the shock classification of eucrites [EPA]

Posted on by

http://arxiv.org/abs/2212.10964


Basaltic rocks occur widely on the terrestrial planets and differentiated asteroids, including the asteroid 4 Vesta. We conducted a shock recovery experiment with decaying compressive pulses on a terrestrial basalt at Chiba Institute of Technology, Japan. The sample recorded a range of pressures, and shock physics modeling was conducted to add a pressure scale to the observed shock features. The shocked sample was examined by optical and electron microscopy, electron back-scattered diffractometry, and Raman spectroscopy. We found that localized melting occurs at a lower pressure (~10 GPa) than previously thought (>20 GPa). The shocked basalt near the epicenter represents shock degree C of a recently proposed classification scheme for basaltic eucrites and, as such, our results provide a pressure scale for the classification scheme. Finally, we estimated the total fraction of the basaltic eucrites classified as shock degree C to be ~15% by assuming the impact velocity distribution onto Vesta.

Read this paper on arXiv…

H. Ono, K. Kurosawa, T. Niihara, et. al.
Thu, 22 Dec 22
25/59

Comments: 17 pages, 4 figures, 1 table, 1 supplementary Information, accepted for publication in Geophysical Research Letters

Radiofrequency Ice Dielectric Measurements at Summit Station, Greenland [CL]

Posted on by

http://arxiv.org/abs/2212.10285


We recently reported on the radio-frequency attenuation length of cold polar ice at Summit Station, Greenland, based on bistatic radar measurements of radio-frequency bedrock echo strengths taken during the summer of 2021. Those data also include echoes attributed to stratified impurities or dielectric discontinuities within the ice sheet (layers), which allow studies of a) estimation of the relative contribution of coherent (discrete layers, e.g.) vs. incoherent (bulk volumetric, e.g.) scattering, b) the magnitude of internal layer reflection coefficients, c) limits on the azimuthal asymmetry of reflections (birefringence), and d) limits on signal dispersion in-ice over a bandwidth of ~100 MHz. We find that i) after averaging 10000 echo triggers, reflected signal observable over the thermal floor (to depths of approximately 1500 m) are consistent with being entirely coherent, ii) internal layer reflection coefficients are measured at approximately -60 to -70 dB, iii) birefringent effects for vertically propagating signals are smaller by an order of magnitude relative to comparable studies performed at South Pole, and iv) within our experimental limits, glacial ice is non-dispersive over the frequency band relevant for neutrino detection experiments.

Read this paper on arXiv…

J. Aguilar, P. Allison, D. Besson, et. al.
Wed, 21 Dec 22
56/81

Comments: N/A

Direct driving of simulated planetary jets by upscale energy transfer [EPA]

Posted on by

http://arxiv.org/abs/2212.09401


The precise mechanism that forms jets and large-scale vortices on the giant planets is unknown. An inverse cascade has been suggested. Alternatively, energy may be directly injected by small-scale convection. Our aim is to clarify whether an inverse cascade feeds zonal jets and large-scale eddies in a system of rapidly rotating, deep, geostrophic spherical-shell convection. We analyze the nonlinear scale-to-scale transfer of kinetic energy in such simulations as a function of the azimuthal wave number, m. We find that the main driving of the jets is associated with upscale transfer directly from the small convective scales to the jets. This transfer is very nonlocal in spectral space, bypassing large-scale structures. The jet formation is thus not driven by an inverse cascade. Instead, it is due to a direct driving by Reynolds stresses from small-scale convective flows. Initial correlations are caused by the effect of uniform background rotation and shell geometry on the flows. While the jet growth suppresses convection, it increases the correlation of the convective flows, which further amplifies the jet growth until it is balanced by viscous dissipation. To a much smaller extent, energy is transferred upscale to large-scale vortices directly from the convective scales, mostly outside the tangent cylinder. There, large-scale vortices are not driven by an inverse cascade either. Inside the tangent cylinder, the transfer to large-scale vortices is weaker, but more local in spectral space, leaving open the possibility of an inverse cascade as a driver of large-scale vortices. In addition, large-scale vortices receive kinetic energy from the jets via forward transfer. We therefore suggest a jet instability as an alternative formation mechanism of largescale vortices. Finally, we find that the jet kinetic energy scales as $\ell^{-5}$, the same as for the zonostrophic regime.

Read this paper on arXiv…

V. Böning, P. Wulff, W. Dietrich, et. al.
Tue, 20 Dec 22
81/97

Comments: 15 pages, 14 figures, accepted for publication in A&A

Liquid Water on Cold Exo-Earths via Basal Melting of Ice Sheets [EPA]

Posted on by

http://arxiv.org/abs/2212.03702


Liquid water is a critical component of habitability. However, the production and stability of surficial liquid water can be challenging on planets outside the Habitable Zone and devoid of adequate greenhouse warming. On such cold, icy exoEarths, basal melting of regional, global ice sheets by geothermal heat provides an alternative means of forming liquid water. Here, we model the thermophysical evolution of ice sheets to ascertain the geophysical conditions that allow liquid water to be produced and maintained at temperatures above the pressure controlled freezing point of water ice on exoEarths. We show that even with a modest, Moon like geothermal heat flow, subglacial oceans of liquid water can form at the base of and within the ice sheets on exoEarths. Furthermore, subglacial oceans may persist on exoEarths for a prolonged period due to the billion year half lives of heat producing elements responsible for geothermal heat. These subglacial oceans, often in contact with the planets crust and shielded from the high energy radiation of their parent star by thick ice layers, may provide habitable conditions for an extended period.

Read this paper on arXiv…

L. Ojha, B. Troncone, J. Buffo, et. al.
Thu, 8 Dec 22
4/63

Comments: N/A

Sunspot periodicity [SSA]

Posted on by

http://arxiv.org/abs/2212.03249


The Schwabe (~11 yr) value for the annual sunspot number is sometimes uncritically applied to other measures of solar activity, direct and indirect, including the 10.7 cm radio flux, the inflow of galactic cosmic rays, solar flare frequency, terrestrial weather, and components of space climate, with the risk of a resulting loss of information. The ruling (Babcock) hypothesis and its derivatives link the sunspot cycle to dynamo processes mediated by differential solar rotation, but despite 60 years of observation and analysis the ~11 yr periodicity remains difficult to model; the possible contribution of planetary dynamics is undergoing a revival. The various solar sequences that genuinely display an ~11 yr cycle stand to benefit from an understanding of its periodicity that goes beyond statistical kinship. The outcome could ironically prompt the demotion of sunspots from their dominant historical role in favour of other possible indicators of solar cyclicity, such as the solar wind flux and its isotopic signatures, even if they are less accessible.

Read this paper on arXiv…

C. Vita-Finzi
Thu, 8 Dec 22
10/63

Comments: 28 pages

The Importance of Co-located VLBI Intensive Stations and GNSS Receivers: A case study of the Maunakea VLBI and GNSS stations during the 2018 Hawai`i earthquake [IMA]

Posted on by

http://arxiv.org/abs/2212.03453


Frequent, low-latency measurements of the Earth’s rotation phase, UT1$-$UTC, critically support the current estimate and short-term prediction of this highly variable Earth Orientation Parameter (EOP). Very Long Baseline Interferometry (VLBI) Intensive sessions provide the required data. However, the Intensive UT1$-$UTC measurement accuracy depends on the accuracy of numerous models, including the VLBI station position. Intensives observed with the Maunakea (Mk) and Pie Town (Pt) stations of the Very Long Baseline Array (VLBA) illustrate how a geologic event (i.e., the $M_w$ 6.9 Hawai`i Earthquake of May 4th, 2018) can cause a station displacement and an associated offset in the values of UT1$-$UTC measured by that baseline, rendering the data from the series useless until it is corrected. Using the non-parametric Nadaraya-Watson estimator to smooth the measured UT1$-$UTC values before and after the earthquake, we calculate the offset in the measurement to be 75.7 $\pm$ 4.6 $\mu$s. Analysis of the sensitivity of the Mk-Pt baseline’s UT1$-$UTC measurement to station position changes shows that the measured offset is consistent with the 67.2 $\pm$ 5.9 $\mu$s expected offset based on the 12.4 $\pm$ 0.6 mm total coseismic displacement of the Maunakea VLBA station determined from the displacement of the co-located global navigation satellite system (GNSS) station. GNSS station position information is known with a latency on the order of tens of hours, and thus can be used to correct the a priori position model of a co-located VLBI station such that it can continue to provide accurate measurements of the critical EOP UT1$-$UTC as part of Intensive sessions. The VLBI station position model would likely not be updated for several months. This contrast highlights the benefit of co-located GNSS and VLBI stations in support of the monitoring of UT1$-$UTC with single baseline Intensives. Abridged.

Read this paper on arXiv…

C. Dieck, M. Johnson and D. MacMillan
Thu, 8 Dec 22
61/63

Comments: 18 pages, 4 figures, accepted for publication in Journal of Geodesy

Investigating the Feasibility of an Impact-Induced Martian Dichotomy [EPA]

Posted on by

http://arxiv.org/abs/2212.02466


A giant impact is commonly thought to explain the dramatic contrast in elevation and crustal thickness between the two hemispheres of Mars known as the “Martian Dichotomy”. Initially, this scenario referred to an impact in the northern hemisphere that would lead to a huge impact basin (dubbed the “Borealis Basin”), while more recent work has instead suggested a hybrid origin that produces the Dichotomy through impact-induced crust-production. The majority of these studies have relied upon impact scaling-laws inaccurate at such large-scales, however, and those that have included realistic impact models have utilised over-simplified geophysical models and neglected any material strength. Here we use a large suite of strength-including smoothed-particle hydrodynamics (SPH) impact simulations coupled with a more sophisticated geophysical scheme of crust production and primordial crust to simultaneously investigate the feasibility of a giant impact on either hemisphere of Mars to have produced its dichotomous crust distribution, and utilise spherical harmonic analysis to identify the best-fitting cases. We find that the canonical Borealis-forming impact is not possible without both excessive crust production and strong antipodal effects not seen on Mars’ southern hemisphere today. Our results instead favour an impact and subsequent localised magma ocean in the southern hemisphere that results in a thicker crust than the north upon crystallisation. Specifically, our best-fitting cases suggest that the projectile responsible for the Dichotomy-forming event was of radius 500-750 km, and collided with Mars at an impact angle of 15-30{\deg} with a velocity of 1.2-1.4 times mutual escape speed ($\sim$6-7 km/s).

Read this paper on arXiv…

H. Ballantyne, M. Jutzi, G. Golabek, et. al.
Tue, 6 Dec 22
81/87

Comments: Accepted for publication in Icarus

Energy budget-based characterization of convection-driven dynamos [CL]

Posted on by

http://arxiv.org/abs/2212.00969


We investigate the energy pathways between the velocity and the magnetic fields in a rotating plane layer dynamo driven by Rayleigh-B\’enard convection using direct numerical simulations. The kinetic and magnetic energies are divided into mean and turbulent components to study the production, transport, and dissipation associated with large and small-scale dynamos. This energy balance-based characterization reveals distinct mechanisms for large- and small-scale magnetic field generation in dynamos, depending on the nature of the velocity field and the conditions imposed at the boundaries.

Read this paper on arXiv…

S. Naskar and A. Pal
Mon, 5 Dec 22
20/63

Comments: N/A

Dynamic reorientation of tidally locked bodies: application to Pluto [EPA]

Posted on by

http://arxiv.org/abs/2212.00880


Planets and moons reorient in space due to mass redistribution associated with various types of internal and external processes. While the equilibrium orientation of a tidally locked body is well understood, much less explored are the dynamics of the reorientation process (or true polar wander, TPW, used here for the motion of either the rotation or the tidal pole). This is despite their importance for predicting the patterns of TPW-induced surface fractures, and for assessing whether enough time has passed for the equilibrium orientation to be reached. The only existing, and relatively complex numerical method for an accurate evaluation of the reorientation dynamics of a tidally locked body was described in a series of papers by Hu et al. (2017a,b, 2019). Here we demonstrate that an identical solution can be obtained with a simple approach, denoted as ow||mMIA, because, contrary to previous claims, during TPW the tidal and the rotation axes closely follow respectively the minor and the major axes of the total, time-evolving inertia tensor. Motivated by the presumed reorientation of Pluto, the use of the ow||mMIA method is illustrated on several test examples. In particular, we analyze whether reorientation paths are curved or straight when the load sign and the mass of the host body are varied. When tidal forcing is relatively small, the paths of negative anomalies (e.g.~basins) towards the rotation pole are highly curved, while positive loads may reach the sub- or anti-host point in a straightforward manner. Our results suggest that the Sputnik Planitia basin cannot be a negative anomaly at present day, and that the remnant figure of Pluto must have formed prior to the reorientation. Finally, the presented method is complemented with an energy balance that can be used to test the numerical solution.

Read this paper on arXiv…

V. Patočka, M. Kihoulou and O. Čadek
Mon, 5 Dec 22
56/63

Comments: 14 pages, 8 figures, to be submitted to Icarus

Statistical Chronometry of Meteorites. II. Initial Abundances and Homogeneity of Short-lived Radionuclides [EPA]

Posted on by

http://arxiv.org/abs/2212.00145


Astrophysical models of planet formation require accurate radiometric dating of meteoritic components by short-lived (Al-Mg, Mn-Cr, Hf-W) and long-lived (U-Pb) chronometers, to develop a timeline of such events in the solar nebula as formation of Ca-rich, Al-rich Inclusions (CAIs), chondrules, planetesimals, etc. CAIs formed mostly around a time (“t=0”) when the short-lived radionuclide 26Al (t1/2 = 0.72 Myr) was present and presumably homogeneously distributed at a known level we define as (26Al/27Al)SS = 5.23 x 10^-5. The time of formation after t=0 of another object can be found by determining its initial (26Al/27Al)0 ratio and comparing it to (26Al/27Al)SS. Dating of meteoritic objects using the Mn-Cr or Hf-W systems is hindered because the abundances (53Mn/55Mn)SS and (182Hf/180Hf)SS at t=0 are not known precisely. To constrain these quantities, we compile literature Al-Mg, Mn-Cr, Hf-W and Pb-Pb data for 13 achondrites and use novel statistical techniques to minimize the discrepancies between their times of formation across these systems. We find that for (53Mn/55Mn)SS = (7.80 +/- 0.36) x 10^-6, (182Hf/180Hf)SS = (10.41 +/- 0.12) x 10^-5, tSS = 4568.65 +/- 0.10 Myr, and a 53Mn half-life of 3.98 +/- 0.22 Myr, these four free parameters make concordant 18 formation times recorded by the different systems in all six known volcanic achondrites (D’Orbigny, SAH 99555, NWA 1670, Asuka 881394, Ibitira, NWA 7325). These parameters also make concordant the ages derived for chondrules from CB/CH achondrites, formed simultaneously in an impact. The other seven achondrites are not quite concordant, but are plutonic angrites or ‘carbonaceous achondrites’ for which simultaneous closure of the isotopic systems might not be expected. Our findings provide very strong support for homogeneity of 26Al, 53Mn and 182Hf in the solar nebula, and our approach offers a path for more precise chronometry.

Read this paper on arXiv…

S. Desch, D. Dunlap, C. Williams, et. al.
Fri, 2 Dec 22
73/81

Comments: Submitted to Geochimica et Cosmochimica Acta

Latitudinal regionalization of rotating spherical shell convection [CL]

Posted on by

http://arxiv.org/abs/2211.17055


Convection occurs ubiquitously on and in rotating geophysical and astrophysical bodies. Prior spherical shell studies have shown that the convection dynamics in polar regions can differ significantly from the lower latitude, equatorial dynamics. Yet most spherical shell convective scaling laws use globally-averaged quantities that erase latitudinal differences in the physics. Here we quantify those latitudinal differences by analyzing spherical shell simulations in terms of their regionalized convective heat transfer properties. This is done by measuring local Nusselt numbers in two specific, latitudinally separate, portions of the shell, the polar and the equatorial regions, $Nu_p$ and $Nu_e$, respectively. In rotating spherical shells, convection first sets in outside the tangent cylinder such that equatorial heat transfer dominates at small and moderate supercriticalities. We show that the buoyancy forcing, parameterized by the Rayleigh number $Ra$, must exceed the critical equatorial forcing by a factor of $\approx 20$ to trigger polar convection within the tangent cylinder. Once triggered, $Nu_p$ increases with $Ra$ much faster than does $Nu_e$. The equatorial and polar heat fluxes then tend to become comparable at sufficiently high $Ra$. Comparisons between the polar convection data and Cartesian numerical simulations reveal quantitative agreement between the two geometries in terms of heat transfer and averaged bulk temperature gradient. This agreement indicates that spherical shell rotating convection dynamics are accessible both through spherical simulations and via reduced investigatory pathways, be they theoretical, numerical or experimental.

Read this paper on arXiv…

T. Gastine and J. Aurnou
Thu, 1 Dec 22
14/85

Comments: 11 pages, 6 figures, accepted for publication in JFM

A field theory approach to the statistical kinematic dynamo [CL]

Posted on by

http://arxiv.org/abs/2211.15827


Variations in the geomagnetic field occur on a vast range of time scales, from milliseconds to millions of years. The advent of satellite measurements has allowed for detailed studies of the short timescale geomagnetic field behaviour, but understanding the long timescale evolution remains challenging due to the sparsity of the paleomagnetic record. This paper introduces a field theory framework for studying magnetic field generation as a result of stochastic fluid motions. By constructing a stochastic kinematic dynamo model, we derive statistical properties of the magnetic field that may be compared to observations from the paleomagnetic record. The fluid velocity is taken to act as a random forcing obeying Gaussian statistics. Using the Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) formalism, we compute the average magnetic field response function. From this we obtain an estimate for the turbulent contribution to the magnetic diffusivity, and find that it is consistent with results from mean-field dynamo theory. This framework presents much promise for studying the geomagnetic field in a stochastic context.

Read this paper on arXiv…

D. Holdenried-Chernoff, D. King and B. Buffett
Wed, 30 Nov 22
23/81

Comments: 22 pages, 6 figures

Solubility of water in peridotite liquids and the prevalence of steam atmospheres on rocky planets [EPA]

Posted on by

http://arxiv.org/abs/2211.13344


Atmospheres are products of time-integrated mass exchange between the surface of a planet and its interior. On Earth and other planetary bodies, magma oceans likely marked significant atmosphere-forming events, during which both steam- and carbon-rich atmospheres may have been generated. However, the nature of Earth’s early atmosphere, and those around other rocky planets, remains unclear for lack of constraints on the solubility of water in liquids of appropriate composition. Here we determine water solubility in 14 peridotite liquids, representative of Earth’s mantle, synthesised in a laser-heated aerodynamic levitation furnace. We explore oxygen fugacities (fO$2$) between -1.9 and +6.0 log units relative to the iron-w\”ustite buffer at constant temperature (2173$\pm$50 K) and total pressure (1 bar). The resulting fH$_2$O ranged from 0 to 0.027 bar and fH$_2$ from 0 to 0.064 bar. Total H$_2$O contents were determined by transmission FTIR spectroscopy from the absorption band at 3550cm$^{-1}$ and applying the Beer-Lambert law. The mole fraction of water in the liquid is $\propto$ (fH$_2$O)$^{0.5}$, attesting to its dissolution as OH. The data are fit by a solubility coefficient of 524$\pm$16 ppmw/bar$^{0.5}$, for a molar absorption coefficient, $\epsilon{3550}$, of 6.3$\pm$0.3 m$^2$/mol in basaltic glasses or 647$\pm$25 ppmw/bar$^{0.5}$, with $\epsilon_{3550}$ = 5.1$\pm$0.3m$^2$/mol for peridotitic glasses. These solubility constants are 10-25 % lower than those for basaltic liquids at 1623 K and 1 bar. Higher temperature lowers water solubility, offsetting the greater depolymerisation of peridotite melts that would otherwise increase H$_2$O solubility relative to basaltic liquids. Because the solubility of water remains high relative to that of CO$_2$, steam atmospheres are rare, although they may form under oxidising conditions on telluric bodies, provided high H/C ratios prevail.

Read this paper on arXiv…

P. Sossi, P. Tollan, J. Badro, et. al.
Mon, 28 Nov 22
78/93

Comments: 13 pages, 9 figures, 2 tables

2D Hybrid method:Case of VLF signal amplitude variations in the time vicinity of an earthquake [CL]

Posted on by

http://arxiv.org/abs/2211.12067


Extraction of information in the form of oscillations from noisy data of natural phenomena such as sounds, earthquakes, ionospheric and brain activity, and various emissions from cosmic objects is extremely difficult. As a method for finding periodicity in such challenging data sets, the 2D Hybrid approach, which employs wavelets, is presented. Our technique produces a wavelet transform correlation intensity contour map for two (or one) time series on a period plane defined by two independent period axes. Notably, by spreading peaks across the second dimension, our method improves apparent resolution of detected oscillations in the period plane and identifies the direction of signal changes using correlation coefficients. We demonstrate the performance of the 2D Hybrid technique on a very low frequency (VLF) signal emitted in Italy and recorded in Serbia in time vicinity of the occurrence of an earthquake on November 3, 2010, near Kraljevo, Serbia. We identified a distinct signal in the range 120-130 s that appears only in association with the considered earthquake. Other wavelets, such as Superlets, which may detect fast transient oscillations, will be employed in the future analysis.

Read this paper on arXiv…

A. Kovacevic, A. Nina, L. Popovic, et. al.
Wed, 23 Nov 22
7/71

Comments: published in Mathematics MDPI

High and dry: billion-year trends in the aridity of river-forming climates on Mars [EPA]

Posted on by

http://arxiv.org/abs/2211.10552


Mars’ wet-to-dry transition is a major environmental catastrophe, yet the spatial pattern, tempo, and cause of drying are poorly constrained. We built a globally-distributed database of constraints on Mars late-stage paleolake size relative to catchment area (aridity index), and found evidence for climate zonation as Mars was drying out. Aridity increased over time in southern midlatitude highlands, where lakes became proportionally as small as in modern Nevada. Meanwhile, intermittently wetter climates persisted in equatorial and northern-midlatitude lowlands. This is consistent with a change in Mars’ greenhouse effect that left highlands too cold for liquid water except during a brief melt season, or alternatively with a fall in Mars’ groundwater table. The data are consistent with a switch of unknown cause in the dependence of aridity index on elevation, from high-and-wet early on, to high-and-dry later. These results sharpen our view of Mars’ climate as surface conditions became increasingly stressing for life.

Read this paper on arXiv…

E. Kite and A. Noblet
Tue, 22 Nov 22
65/83

Comments: Accepted by Geophysical Research Letters

Surviving in Ocean Worlds: Experimental Characterization of Fiber Optic Tethers across Europa-like Ice Faults and Unraveling the Sliding Behavior of Ice [EPA]

Posted on by

http://arxiv.org/abs/2211.10337


As an initial step towards in-situ exploration of the interiors of Ocean Worlds to search for life using cryobot architectures, we test how various communication tethers behave under potential Europa-like stress conditions. By freezing two types of pretensioned insulated fiber optic cables inside ice blocks, we simulate tethers being refrozen in a probe’s wake as it traverses through an Ocean World’s ice shell. Using a cryogenic biaxial apparatus, we simulate shear motion on pre-existing faults at various velocities and temperatures. These shear tests are used to evaluate the mechanical behavior of ice, characterize the behavior of communication tethers, and explore their limitations for deployment by a melt probe. We determine (a) the maximum shear stress tethers can sustain from an ice fault, prior to failure (viable/unviable regimes for deployment) and (b) optical tether performance for communications. We find that these tethers are fairly robust across a range of temperature and velocity conditions expected on Europa (T(K) = 95 to 260; velocity (m/s) = 5 x 10-7 to 3 x 10-4). However, damage to the outer jackets of the tethers and stretching of inner fibers at the coldest temperatures tested both indicate a need for further tether prototype development.
Overall, these studies constrain the behavior of optical tethers for use at Ocean Worlds, improve the ability to probe thermomechanical properties of dynamic ice shells likely to be encountered by landed missions, and guide future technology development for accessing the interiors of (potentially habitable / inhabited) Ocean Worlds.

Read this paper on arXiv…

V. Singh, C. McCarthy, M. Silvia, et. al.
Mon, 21 Nov 22
10/66

Comments: N/A

Exploring Earth's Ionosphere and its effect on low radio frequency observation with the uGMRT and the SKA [EPA]

Posted on by

http://arxiv.org/abs/2211.09738


The Earth’s ionosphere introduces systematic effects that limit the performance of a radio interferometer at low frequencies ($\lesssim 1$\,GHz). These effects become more pronounced for severe geomagnetic activities or observations involving longer baselines of the interferometer. The uGMRT, a pathfinder for the Square Kilometre Array (SKA), is located in between the northern crest of the Equatorial Ionisation Anomaly (EIA) and the magnetic equator. Hence, this telescope is more prone to severe ionospheric conditions and is a unique radio interferometer for studying the ionosphere. Here, we present 235\,MHz observations with the GMRT, showing significant ionospheric activities over a solar minimum. In this work, we have characterised the ionospheric disturbances observed with the GMRT and compared them with ionospheric studies and observations with other telescopes like the VLA, MWA and LOFAR situated at different magnetic latitudes. We have estimated the ionospheric total electron content (TEC) gradient over the full GMRT array which shows an order of magnitude higher sensitivity compared to the Global Navigation Satellite System (GNSS). Furthermore, this article uses the ionospheric characteristics estimated from the observations with uGMRT, VLA, LOFAR and MWA to forecast the effects on the low-frequency observations with the SKA1-MID and SKA1-LOW in future.

Read this paper on arXiv…

S. Mangla, S. Chakraborty, A. Datta, et. al.
Fri, 18 Nov 22
61/70

Comments: 15 Pages, 10 figures, 2 Tables, accepted for publication in The Journal of Astrophysics and Astronomy

The Dissipation of the Solar Nebula Constrained by Impacts and Core Cooling in Planetesimals [EPA]

Posted on by

http://arxiv.org/abs/2211.08306


Rapid cooling of planetesimal cores has been inferred for several iron meteorite parent bodies based on metallographic cooling rates, and linked to the loss of their insulating mantles during impacts. However, the timing of these disruptive events is poorly constrained. Here, we used the short-lived 107Pd / 107Ag decay system to date rapid core cooling by determining Pd-Ag ages for iron meteorites. We show closure times for the iron meteorites equate to cooling in the timeframe ~7.8 to 11.7 Myr after CAI, and indicate that an energetic inner Solar System persisted at this time. This likely results from the dissipation of gas in the protoplanetary disk, after which the damping effect of gas drag ceases. An early giant planet instability between 5 and 14 Myr after CAI could have reinforced this effect. This correlates well with the timing of impacts recorded by the Pd Ag system for iron meteorites.

Read this paper on arXiv…

A. Hunt, K. Theis, M. Rehkämper, et. al.
Wed, 16 Nov 22
54/76

Comments: 3 tables, 2 figures, 3 extended data figures, 1 supplementary table

Solar storms and submarine internet cables [CL]

Posted on by

http://arxiv.org/abs/2211.07850


Coronal mass ejections (CMEs) can trigger geomagnetic storms and induce geoelectric currents that degrade the performance of terrestrial power grid operations; in particular, CMEs are known for causing large-scale outages in electrical grids. Submarine internet cables are powered through copper conductors spanning thousands of kilometers and are vulnerable to damage from CMEs, raising the possibility of a large-scale and long-lived internet outage. To better understand the magnitude of these risks, we monitor voltage changes in the cable power supply of four different transoceanic cables during time periods of high solar activity. We find a strong correlation between the strength of the high-frequency geomagnetic field at the landing sites of the systems and the line voltage change. We also uncover that these two quantities exhibit a near-linear power law scaling behavior that allows us to estimate the effects of once-in-a-century CME events. Our findings reveal that long-haul submarine cables, regardless of their length and orientation, will not be damaged during a solar superstorm, even one as large as the 1859 Carrington event.

Read this paper on arXiv…

J. Castellanos, J. Conroy, V. Kamalov, et. al.
Wed, 16 Nov 22
70/76

Comments: 19 pages, 5 figures

VLBI Celestial and Terrestrial Reference Frames VIE2022b [IMA]

Posted on by

http://arxiv.org/abs/2211.07338


Context: We introduce the computation of global reference frames from Very Long Baseline Interferometry (VLBI) observations at the Vienna International VLBI Service for Geodesy and Astrometry (IVS) Analysis Center (VIE) in detail. We focus on the celestial and terrestrial frames from our two latest solutions VIE2020 and VIE2022b. Aims: The current International Celestial and Terrestrial Reference Frames, ICRF3 and ITRF2020, include VLBI observations until spring 2018 and December 2020, respectively. We provide terrestrial and celestial reference frames including VLBI sessions until June 2022 organized by the IVS. Methods: Vienna terrestrial and celestial reference frames are computed in a common least squares adjustment of geodetic and astrometric VLBI observations with the Vienna VLBI and Satellite Software (VieVS). Results: We provide high-quality celestial and terrestrial reference frames computed from 24-hour IVS observing sessions. The CRF provides positions of 5407 radio sources. In particular, positions of sources with few observations at the time of the ICRF3 calculation could be improved. The frame also includes positions of 870 new radio sources, which are not included in ICRF3. The additional observations beyond the data used for ITRF2020 provide a more reliable estimation of positions and linear velocities of newly established VLBI Global Observing System (VGOS) telescopes.

Read this paper on arXiv…

H. Krásná, L. Baldreich, J. Böhm, et. al.
Tue, 15 Nov 22
47/103

Comments: 11 pages, Submitted to the Astronomy & Astrophysics

Rapid Formation of Exoplanetesimals Revealed by White Dwarfs [EPA]

Posted on by

http://arxiv.org/abs/2211.07244


The timing of formation for the first planetesimals determines the mode of planetary accretion and their geophysical and compositional evolution. Astronomical observations of circumstellar discs and Solar System geochronology provide evidence for planetesimal formation during molecular cloud collapse, much earlier than previously estimated. Here, we present distinct observational evidence from white dwarf planetary systems for planetesimal formation occurring during the first few hundred thousand years after cloud collapse in exoplanetary systems. A significant fraction of white dwarfs have accreted planetary material rich in iron core or mantle material. In order for the exo-asteroids accreted by white dwarfs to form iron cores, substantial heating is required. By simulating planetesimal evolution and collisional evolution we show that the most likely heat source is short-lived radioactive nuclides such as Al-2 (half life of approximately 0.7 Myr). Core-rich materials in the atmospheres of white dwarfs, therefore, provide independent evidence for rapid planetesimal formation, concurrent with star formation.

Read this paper on arXiv…

A. Bonsor, T. Lichtenberg, J. Drazkowska, et. al.
Tue, 15 Nov 22
67/103

Comments: Accepted to Nature Astronomy

Interior heating of rocky exoplanets from stellar flares with application to TRAPPIST-1 [EPA]

Posted on by

http://arxiv.org/abs/2211.06140


Many stars of different spectral types with planets in the habitable zone are known to emit flares. Until now, studies that address the long-term impact of stellar flares and associated Coronal Mass Ejections (CMEs) assumed that the planet’s interior remains unaffected by interplanetary CMEs, only considering the effect of plasma/UV interactions on the atmosphere of planets. Here, we show that the magnetic flux carried by flare-associated CMEs results in planetary interior heating by Ohmic dissipation and leads to a variety of interior–exterior interactions. We construct a physical model to study this effect and apply it to the TRAPPIST-1 star whose flaring activity has been constrained by Kepler observations. Our model is posed in a stochastic manner to account for uncertainty and variability in input parameters. Particularly for the innermost planets, our results suggest that the heat dissipated in the silicate mantle is both of sufficient magnitude and longevity to drive geological processes and hence facilitate volcanism and outgassing of the TRAPPIST-1 planets. Furthermore, our model predicts that Joule heating can further be enhanced for planets with an intrinsic magnetic field compared to those without. The associated volcanism and outgassing may continuously replenish the atmosphere and thereby mitigate the erosion of the atmosphere caused by the direct impact of flares and CMEs. To maintain consistency of atmospheric and geophysical models, the impact of stellar flares and CMEs on atmospheres of close-in exoplanetary systems needs to be studied in conjunction with the effect on planetary interiors.

Read this paper on arXiv…

A. Grayver, D. Bower, J. Saur, et. al.
Mon, 14 Nov 22
44/69

Comments: N/A

Single band VLBI absolute astrometry [IMA]

Posted on by

http://arxiv.org/abs/2211.04647


The ionospheric path delay impacts single-band very long baseline interferometry (VLBI) group delays, which limits their applicability for absolute astrometry. I consider two important cases: when observations are made simultaneously at two bands, but delays at only one band are available for a subset of observations and when observations are made at one band only by design. I developed optimal procedures of data analysis for both cases using Global Navigation Satellite System (GNSS) ionosphere maps, provided a stochastic model that describes ionospheric errors, and evaluated their impact on source position estimates. I demonstrate that the stochastic model is accurate at a level of 15%. I found that using GNSS ionospheric maps as is introduces serious biases in estimates of declinations and I developed the procedure that almost eliminates them. I found serendipitously that GNSS ionospheric maps have multiplicative errors and have to be scaled by 0.85 in order to mitigate the declination bias. A similar scale factor was found in comparison of the vertical total electron contents from satellite altimetry against GNSS ionospheric maps. I favor interpretation of this scaling factor as a manifestation of the inadequacy of the thin shell model. I showed in this study that we are able to model the ionospheric path delay to the extent that no systematic errors emerge and we are able to adequately assess the contribution of the ionosphere-driven random errors on source positions. This makes single-band absolute astrometry a viable option that can be used for source position determination.

Read this paper on arXiv…

L. Petrov
Thu, 10 Nov 22
21/78

Comments: Submitted to the Astronomical Journal

Planetary Exploration Horizon 2061 Report, Chapter 3: From science questions to Solar System exploration [IMA]

Posted on by

http://arxiv.org/abs/2211.04474


This chapter of the Planetary Exploration Horizon 2061 Report reviews the way the six key questions about planetary systems, from their origins to the way they work and their habitability, identified in chapter 1, can be addressed by means of solar system exploration, and how one can find partial answers to these six questions by flying to the different provinces to the solar system: terrestrial planets, giant planets, small bodies, and up to its interface with the local interstellar medium. It derives from this analysis a synthetic description of the most important space observations to be performed at the different solar system objects by future planetary exploration missions. These observation requirements illustrate the diversity of measurement techniques to be used as well as the diversity of destinations where these observations must be made. They constitute the base for the identification of the future planetary missions we need to fly by 2061, which are described in chapter 4. Q1- How well do we understand the diversity of planetary systems objects? Q2- How well do we understand the diversity of planetary system architectures? Q3- What are the origins and formation scenarios for planetary systems? Q4- How do planetary systems work? Q5- Do planetary systems host potential habitats? Q6- Where and how to search for life?

Read this paper on arXiv…

V. Dehant, M. Blanc, S. Mackwell, et. al.
Thu, 10 Nov 22
34/78

Comments: 107 pages, 37 figures, Horizon 2061 is a science-driven, foresight exercise, for future scientific investigations

Thermal energy budget of electrons in the inner heliosphere: Parker Solar Probe Observations [SSA]

Posted on by

http://arxiv.org/abs/2211.02186


We present an observational analysis of the electron thermal energy budget using data from Parker Solar Probe. We use the macroscopic moments, obtained from our fits to the measured electron distribution function, to evaluate the thermal energy budget based on the second moment of the Boltzmann equation. We separate contributions to the overall budget from reversible and irreversible processes. We find that a thermal-energy source must be present in the inner heliosphere over the heliocentric distance range from 0.15 to 0.47 au. The divergence of the heat flux is positive at heliocentric distances below 0.33 au, while beyond 0.33 au, there is a measurable degradation of the heat flux. Expansion effects dominate the thermal energy budget below 0.3 au. Under our steady-state assumption, the free streaming of the electrons is not sufficient to explain the thermal energy density budget. We conjecture that the most likely driver for the required heating process is turbulence. Our results are consistent with the known non-adiabatic polytropic index of the electrons, which we measure as 1.176 in the explored range of heliocentric distances.

Read this paper on arXiv…

J. Abraham, D. Verscharen, R. T.Wicks, et. al.
Mon, 7 Nov 22
53/67

Comments: Paper accepted to The Astrophysical Journal

A study of global magnetic helicity in self-consistent spherical dynamos [SSA]

Posted on by

http://arxiv.org/abs/2211.01356


Magnetic helicity is a fundamental constraint in both ideal and resistive magnetohydrodynamics. Measurements of magnetic helicity density on the Sun and other stars are used to interpret the internal behaviour of the dynamo generating the global magnetic field. In this note, we study the behaviour of the global relative magnetic helicity in three self-consistent spherical dynamo solutions of increasing complexity. Magnetic helicity describes the global linkage of the poloidal and toroidal magnetic fields (weighted by magnetic flux), and our results indicate that there are preferred states of this linkage. This leads us to propose that global magnetic reversals are, perhaps, a means of preserving this linkage, since, when only one of the poloidal or toroidal fields reverses, the preferred state of linkage is lost. It is shown that magnetic helicity indicates the onset of reversals and that this signature may be observed at the outer surface.

Read this paper on arXiv…

P. Gupta, R. Simitev and D. MacTaggart
Thu, 3 Nov 22
26/59

Comments: To appear in Geophysical and Astrophysical Fluid Dynamics [Accepted 2022-10-14]

The Age and Erosion Rate of Young Sedimentary Rock on Mars [EPA]

Posted on by

http://arxiv.org/abs/2211.00236


The Medusae Fossae Formation (MFF) is an enigmatic sedimentary unit near the equator of Mars, with an uncertain formation process and absolute age. Due to the heavily wind-eroded surface, it is difficult to determine the absolute model age of the MFF using a one-parameter model based on the crater size-frequency distribution function with existing crater count data. We create a new two-parameter model that estimates both age and a constant erosion rate ($\beta$) by treating cratering as a random Poisson process. Our study uses new crater count data collected from Context Camera imagery for both the MFF and other young equatorial sedimentary rock. Based on our new model, the Central MFF formed $>$1.5 Gyr ago and had low erosion rates ($<$650 nm yr$^{-1}$), whereas the East MFF, Far East MFF, and Zephyria Planum most likely formed $<$1.5 Gyr ago and had higher erosion rates ($>$740 nm $^{-1}$). The top of Aeolis Mons (informally known as Mount Sharp) in Gale Crater and Eastern Candor have relatively young ages and low erosion rates. Based on the estimated erosion rates (since fast erosion permits metastable shallow ice), we also identify several sites, including Zephyria Planum, as plausible locations for shallow subsurface equatorial water ice that is detectable by gamma-ray spectroscopy or neutron spectroscopy. In addition to confirming $<$1.5 Gyr sedimentary rock formations on Mars, and distinguishing older and younger MFF sites, we find that fast-eroding locations have younger ages and MFF locations with slower erosion have older best-fit ages.

Read this paper on arXiv…

A. Li, E. Kite and K. Keating
Wed, 2 Nov 22
59/67

Comments: 17 pages, 12 figures

Metal-silicate partitioning of W and Mo and the role of carbon in controlling their abundances in the Bulk Silicate Earth [EPA]

Posted on by

http://arxiv.org/abs/2210.14028


The liquid metal-liquid silicate partitioning of molybdenum and tungsten during core formation must be well-constrained in order to understand the evolution of Earth and other planetary bodies, in particular because the Hf-W isotopic system is used to date early planetary evolution. We combine 48 new high pressure and temperature experimental results with a comprehensive database of previous experiments to re-examine the systematics of Mo and W partitioning. W partitioning is particularly sensitive to silicate and metallic melt compositions and becomes more siderophile with increasing temperature. We show that W has a 6+ oxidation state in silicate melts over the full experimental fO2 range of $\Delta$IW -1.5 to -3.5. Mo has a 4+ oxidation state and its partitioning is less sensitive to silicate melt composition, but also depends on metallic melt composition. DMo stays approximately constant with increasing depth in Earth. Both W and Mo become more siderophile with increasing C content of the metal, so we fit epsilon interaction parameters. W and Mo along with C are incorporated into a combined N-body accretion and core-mantle differentiation model. We show that W and Mo require the early accreting Earth to be sulfur-depleted and carbon-enriched so that W and Mo are efficiently partitioned into Earth’s core and do not accumulate in the mantle. If this is the case, the produced Earth-like planets possess mantle compositions matching the BSE for all simulated elements. However, there are two distinct groups of estimates of the bulk mantle’s C abundance in the literature: low (100 ppm), and high (800 ppm), and all models are consistent with the higher estimated carbon abundance. The low BSE C abundance would be achievable when the effects of the segregation of dispersed metal droplets produced in deep magma oceans by the disproportionation of Fe2+ to Fe3+ plus metallic Fe is considered.

Read this paper on arXiv…

E. Jennings, S. Jacobson, D. Rubie, et. al.
Wed, 26 Oct 22
69/73

Comments: 61 pages including supplemental material

Modelling Cosmic Radiation Events in the Tree-ring Radiocarbon Record [SSA]

Posted on by

http://arxiv.org/abs/2210.13775


Annually-resolved measurements of the radiocarbon content in tree-rings have revealed rare sharp rises in carbon-14 production. These ‘Miyake events’ are likely produced by rare increases in cosmic radiation from the Sun or other energetic astrophysical sources. The radiocarbon produced is not only circulated through the Earth’s atmosphere and oceans, but also absorbed by the biosphere and locked in the annual growth rings of trees. To interpret high-resolution tree-ring radiocarbon measurements therefore necessitates modelling the entire global carbon cycle. Here, we introduce ‘ticktack’, the first open-source Python package that connects box models of the carbon cycle with modern Bayesian inference tools. We use this to analyse all public annual 14C tree data, and infer posterior parameters for all six known Miyake events. They do not show a consistent relationship to the solar cycle, and several display extended durations that challenge either astrophysical or geophysical models.

Read this paper on arXiv…

Q. Zhang, U. Sharma, J. Dennis, et. al.
Wed, 26 Oct 22
71/73

Comments: Accepted Proceedings of the Royal Society A. 19 pages 6 figures body, 12 pages appendices which are supplementary material in the published version

Interplay between geostrophic vortices and inertial waves in precession-driven turbulence [CL]

Posted on by

http://arxiv.org/abs/2210.12536


The properties of rotating turbulence driven by precession are studied using direct numerical simulations and analysis of the underlying dynamical processes in Fourier space. The study is carried out in the local rotating coordinate frame, where precession gives rise to a background shear flow, which becomes linearly unstable and breaks down into turbulence. We observe that this precession-driven turbulence is in general characterized by coexisting two dimensional (2D) columnar vortices and three dimensional (3D) inertial waves, whose relative energies depend on the precession parameter $Po$. The vortices resemble the typical condensates of geostrophic turbulence, are aligned along the rotation axis (with zero wavenumber in this direction, $k_z=0$) and are fed by the 3D waves through nonlinear transfer of energy, while the waves (with $k_z\neq0$) in turn are directly fed by the precessional instability of the background flow. The vortices themselves undergo inverse cascade of energy and exhibit anisotropy in Fourier space. For small $Po<0.1$ and sufficiently high Reynolds numbers, the typical regime for most geo- and astrophysical applications, the flow exhibits strongly oscillatory (bursty) evolution due to the alternation of vortices and small-scale waves. On the other hand, at larger $Po>0.1$ turbulence is quasi-steady with only mild fluctuations, the coexisting columnar vortices and waves in this state give rise to a split (simultaneous inverse and forward) cascade. Increasing the precession magnitude causes a reinforcement of waves relative to vortices with the energy spectrum approaching Kolmogorov scaling and, therefore, the precession mechanism counteracts the effects of the rotation.

Read this paper on arXiv…

F. Pizzi, G. Mamatsashvili, A. Barker, et. al.
Tue, 25 Oct 22
93/111

Comments: 20 pages, 16 figures, 1 table, submitted to Physics of Fluids

The effect of collisional erosion on the composition of Earth-analog planets in Grand Tack models: Implications for the formation of the Earth [EPA]

Posted on by

http://arxiv.org/abs/2210.11896


Impact-induced erosion of the Earth’s early crust during accretion of terrestrial bodies can significantly modify the primordial chemical composition of the Bulk Silicate Earth (BSE, that is, the composition of the crust added to the present-day mantle). In particular, it can be particularly efficient in altering the abundances of elements having a strong affinity for silicate melts (i.e. incompatible elements) as the early differentiated crust was preferentially enriched in those. Here, we further develop an erosion model (EROD) to quantify the effects of collisional erosion on the final composition of the BSE. Results are compared to the present-day BSE composition models and constraints on Earth’s accretion processes are provided. The evolution of the BSE chemical composition resulting from crustal stripping is computed for entire accretion histories of about 50 Earth analogs in the context of the Grand Tack model. The chosen chemical elements span a wide range of incompatibility degrees. We find that a maximum loss of 40wt% can be expected for the most incompatible lithophile elements such as Rb, Th or U in the BSE when the crust is formed from low partial melting rates. Accordingly, depending on both the exact nature of the crust-forming processes during accretion and the accretion history itself, Refractory Lithophile Elements (RLE) may not be in chondritic relative proportions in the BSE. In that case, current BSE estimates may need to be corrected as a function of the geochemical incompatibility of these elements. Alternatively, if RLE are indeed in chondritic relative proportions in the BSE, accretion scenarios that are efficient in affecting the BSE chemical composition should be questioned.

Read this paper on arXiv…

A. L., S. J., C. S., et. al.
Mon, 24 Oct 22
24/56

Comments: 40 pages all included, 5 figures, accepted in Icarus

LavAtmos: An open source chemical equilibrium vaporisation code for lava worlds [EPA]

Posted on by

http://arxiv.org/abs/2210.10463


To date, over 500 short-period rocky planets with equilibrium temperatures above 1500 K have been discovered. Such planets are expected to support magma oceans, providing a direct interface between the interior and atmosphere. This provides a unique opportunity to gain insight into their interior compositions through atmospheric observations. A key process in doing such work is the vapor outgassing from the lava surface. LavAtmos is an open-source code that calculates the equilibrium chemical composition of vapor above a melt for a given composition and temperature. Results show that the produced output is in good agreement with the partial pressures obtained from experimental laboratory data as well as with other similar codes from literature. LavAtmos allows for the modeling of vaporisation of a wide range of different mantle compositions of hot-rocky exoplanets. In combination with atmospheric chemistry codes, this enables the characterization of interior compositions through atmospheric signatures.

Read this paper on arXiv…

C. Buchem, Y. Miguel, M. Zilinskas, et. al.
Thu, 20 Oct 22
66/74

Comments: 26 pages, 6 figures, submitted to the Journal of Computational Chemistry

Expected geoneutrino signal at JUNO using local integrated 3-D refined crustal model [CL]

Posted on by

http://arxiv.org/abs/2210.09165


Geoneutrinos are a unique tool that brings to the surface information about our planet, in particular, its radiogenic power, insights formation and chemical composition. To date, only the KamLAND and Borexino experiments observed geoneutrino, with the former characterized by low concentration of heat-producing elements in the Earth in contrast to the latter that sets tight upper limits on the power of a georeactor hypothesized. With respect to the results yielded therefrom, a small discrepancy has been identified. On this account, next generation experiments like JUNO are needed if it is to provide definitive results with respect to the Earth’s radiogenic power, and to fully exploit geoneutrinos to better understand deep Earth.
An accurate a priori prediction of the crustal contribution plays an important role in enabling the translation of a particle physics measurement into geo-scientific questions. The existing GIGJ model of JUNO only focused on constructing a geophysical model of the local crust, without local geochemical data. Another existing JULOC includes both data, but only able to be achieved for the top layer of the upper crust, not in deep vertical. This paper reports on the development of JUNO’s first 3-D integrated model, JULOC-I, which combines seismic, gravity, rock sample and thermal flow data with new building method, solved the problem in vertical depth.
JULOC-I results show higher than expected geoneutrino signals are mainly attributable to higher U and Th in southern China than that found elsewhere on Earth. Moreover, the high level of accuracy of the JULOC-I model, complemented by 10 years of experimental data, indicates that JUNO has an opportunity to test different mantle models. Predictions by JULOC-I can be tested after JUNO goes online and higher accuracy local crustal model continue to play an important role to improve mantle measurements precision.

Read this paper on arXiv…

R. Han, Z. Li, R. Gao, et. al.
Tue, 18 Oct 22
50/99

Comments: 26 pages, 10 figures

Lithospheric loading model for large impact basin where mantle plug presents [EPA]

Posted on by

http://arxiv.org/abs/2210.05428


Lithosphere is the outer rigid part of terrestrial body, usually consisting of the crust and part of the mantle. Characterizing the physical properties of lithosphere is critical in the investigation to its evolution history. Through the modeling of mass-related loads within lithosphere, physical parameters such as elastic thickness of lithosphere can be inferred by gravity and topography data. At impact basin region, however, the low correlation between topography and gravity makes this model inapplicable. In this work, we proposed a loading model incorporated with the mantle uplift structure commonly formed at impact basin. The resulting deflection caused by this mantle uplift structure is also modeled in the governing equation of the thin elastic shell. Gravity anomaly of the deflected lithosphere is calculated at the surface and the crustal-mantle boundary, then the theoretical gravity admittance and correlation can be compared with observed data. The application of the mantle loading model at four large impact basins on Mars show better fit to the observed admittance and correlation compared with loading model that without this initial mantle plug. Our work suggests that proper modeling of impact-induced load and its resulting deflection is the key to the understanding of physical properties of planetary lithosphere at basin region.

Read this paper on arXiv…

Q. Deng, Z. Zhong, M. Ye, et. al.
Wed, 12 Oct 22
72/75

Comments: N/A

Lava World: Exoplanet Surfaces [EPA]

Posted on by

http://arxiv.org/abs/2210.03056


The recent first measurements of the reflection of the surface of a lava world provides an unprecedented opportunity to investigate different stages of rocky planet evolution. The spectral features of the surfaces of rocky lava world exoplanets give insights into their evolution, mantle composition and inner workings. However, no database exists yet that contains spectral reflectivity and emission of a wide range of potential exoplanet surface materials. Here we first synthesized 16 potential exoplanet surfaces, spanning a wide range of chemical compositions based on potential mantle material guided by the metallicity of different host stars. Then we measured their infrared reflection spectrum (2.5 – 28 {\mu}m, 350 – 4000 cm^{-1}), from which we can obtain their emission spectra and establish the link between the composition and a strong spectral feature at 8 {\mu}m, the Christiansen feature (CF). Our analysis suggests a new multi-component composition relationship with the CF, as well as a correlation with the silica content of the exoplanet mantle. We also report the mineralogies of our materials as possibilities for that of lava worlds. This database is a tool to aid in the interpretation of future spectra of lava worlds that will be collected by the James Webb Space Telescope and future missions

Read this paper on arXiv…

M. Fortin, E. Gazel, L. Kaltenegger, et. al.
Fri, 7 Oct 22
58/62

Comments: published in Monthly Notices of the Royal Astronomical Society

Cross-Wave Profiles of Altitude and Particle Size of Noctilucent Clouds in the Case of One-Dimensional Small-Scale Gravity Wave Pattern [CL]

Posted on by

http://arxiv.org/abs/2210.00431


This paper describes the wide-field three-color observations of an expanded field of noctilucent clouds modulated by a one-dimensional gravity wave. Long wave crests were aligned by a small angle to the solar vertical in the sky. This made possible separate determination of altitude and particle size at different wave phases based on three-color photometry of noctilucent clouds. Thereby, it is possible to use simple optical imaging to record the changes in the parameters of noctilucent clouds when a short-period gravity wave passes by.

Read this paper on arXiv…

O. Ugolnikov
Tue, 4 Oct 22
70/71

Comments: 8 pages, 6 figures, submitted to Planetary and Space Science

GENESIS: Co-location of Geodetic Techniques in Space [CL]

Posted on by

http://arxiv.org/abs/2209.15298


Improving and homogenizing time and space reference systems on Earth and, more directly, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1mm and a long-term stability of 0.1mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities which has enunciated geodesy requirements for Earth sciences.
Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, proposed as a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this white paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology.

Read this paper on arXiv…

P. Delva, Z. Altamimi, A. Blazquez, et. al.
Mon, 3 Oct 22
38/55

Comments: 31 pages, 9 figures, submitted to Earth, Planets and Space (EPS)

Modification of the radioactive heat budget of Earth-like exoplanets by the loss of primordial atmospheres [EPA]

Posted on by

http://arxiv.org/abs/2209.14691


The initial abundance of radioactive heat producing isotopes in the interior of a terrestrial planet are important drivers of its thermal evolution and the related tectonics and possible evolution to an Earth-like habitat. The moderately volatile element K can be outgassed from a magma ocean into H$2$-dominated primordial atmospheres of protoplanets with assumed masses between 0.55-1.0$ M{\rm Earth}$ at the time when the gas disk evaporated. We estimate this outgassing and let these planets grow through impacts of depleted and non-depleted material that resembles the same $^{40}$K abundance of average carbonaceous chondrites until the growing protoplanets reach 1.0 $M_{\rm Earth}$. We examine different atmospheric compositions and, as a function of pressure and temperature, calculate the proportion of K by Gibbs Free Energy minimisation using the GGChem code. We find that for H$_2$-envelopes and for magma ocean surface temperatures that are $\ge$ 2500 K, no K condensates are thermally stable, so that outgassed $^{40}$K can populate the atmosphere to a great extent. However, due to magma ocean turn-over time and the limited diffusion of $^{40}$K into the upper atmosphere, from the entire $^{40}$K in the magma ocean only a fraction may be available for escaping into space. The escape rates of the primordial atmospheres and the dragged $^{40}$K are further simulated for different stellar EUV-activities with a multispecies hydrodynamic upper atmosphere evolution model. Our results lead to different abundances of heat producing elements within the fully grown planets which may give rise to different thermal and tectonic histories of terrestrial planets and their habitability conditions.

Read this paper on arXiv…

N. Erkaev, M. Scherf, O. Herbort, et. al.
Fri, 30 Sep 22
15/71

Comments: 22 pages, 11 figures. This is a preprint of a 2nd revision submitted to MNRAS

Reduced late bombardment on rocky exoplanets around M-dwarfs [EPA]

Posted on by

http://arxiv.org/abs/2209.14037


Ocean-vaporizing impacts of chemically reduced planetesimals onto the early Earth have been suggested to catalyse atmospheric production of reduced nitrogen compounds and trigger prebiotic synthesis despite an oxidized lithosphere. While geochemical evidence supports a dry, highly reduced late veneer on Earth, the composition of late-impacting debris around lower-mass stars is subject to variable volatile loss as a result of their hosts’ extended pre-main sequence phase. We perform simulations of late-stage planet formation across the M-dwarf mass spectrum to derive upper limits on reducing bombardment epochs in Hadean analog environments. We contrast the Solar System scenario with varying initial volatile distributions due to extended primordial runaway greenhouse phases on protoplanets and desiccation of smaller planetesimals by internal radiogenic heating. We find a decreasing rate of late-accreting reducing impacts with decreasing stellar mass. Young planets around stars $\leq$ 0.4 $M_\odot$ experience no impacts of sufficient mass to generate prebiotically relevant concentrations of reduced atmospheric compounds once their stars have reached the main sequence. For M-dwarf planets to not exceed Earth-like concentrations of volatiles, both planetesimals and larger protoplanets must undergo extensive devolatilization processes and can typically emerge from long-lived magma ocean phases with sufficient atmophile content to outgas secondary atmospheres. Our results suggest that transiently reducing surface conditions on young rocky exoplanets are favoured around FGK- stellar types relative to M-dwarfs.

Read this paper on arXiv…

T. Lichtenberg and M. Clement
Thu, 29 Sep 22
58/70

Comments: 17 pages, 3 figures, 1 table; accepted for publication in ApJL

Analysis and Modeling of High-Frequency Emission and Deep Seismic Sources of Sunquakes [SSA]

Posted on by

http://arxiv.org/abs/2209.11286


Recent work published by Lindsey et al find evidence for a deep and compact seismic source for the sunquake associated with the 2011 July 30 M9.3 flare, as well as seismic emission extending up to 10 mHz. We examine the sunquake independently, and a possible wavefront is found in the 8 mHz band, though no wavefront is easily discernible in the 10 mHz band. Additionally, we perform numerical simulations of seismic excitation modeled with the reported parameters and changes in the power spectra with increasing depth of the excitation source are examined. It is found that the peak frequency decreases for increasing depths, but a shallow minimum is indicated between z=0 and z=-840 km. Analysis of the suspected wavefront of the M9.3 sunquake finds that the power spectrum of the reported seismic emission is close to that of background oscillations, though with a peak frequency noticeably lower than the background peak. Additionally, it is found that the amplitude of the source estimated by Lindsey et al is too low to produce the observed wavefront.

Read this paper on arXiv…

J. Stefan and A. Kosovichev
Mon, 26 Sep 22
16/62

Comments: N/A

Transmission of a Seismic Wave generated by impacts on Granular Asteroids [EPA]

Posted on by

http://arxiv.org/abs/2209.11353


In this paper we use a Soft-Sphere Discrete Element method code to simulate the transmission and study the attenuation of a seismic wave. Then, we apply our findings to the different space missions that have had to touch the surface of different small bodies. Additionally, we do the same in regards to the seismic wave generated by the hypervelocity impacts produced by the DART and Hayabusa2 missions once the shock wave transforms into a seismic wave. We find that even at very low pressures, such as those present in the interior of asteroids, the seismic wave speed can still be on the order of hundreds of m/s depending on the velocity of the impact that produces the wave. As expected from experimental measurements, our results show that wave velocity is directly dependent on $P^{1/6}$, where $P$ is the total pressure (confining pressure plus wave induced pressure). Regardless of the pressure of the system and the velocity of the impact (in the investigated range), energy dissipation is extremely high. These results provide us with a way to anticipate the extent to which a seismic wave could have been capable of moving some small particles on the surface of a small body upon contact with a spacecraft. Additionally, this rapid energy dissipation would imply that even hypervelocity impacts should perturb only the external layer of a self-gravitating aggregate on which segregation and other phenomena could take place. This would in turn produce a layered structure of which some evidence has been observed

Read this paper on arXiv…

P. Sánchez, D. Scheeres and A. Quillen
Mon, 26 Sep 22
43/62

Comments: Accepted for publication in The Planetary Sciences Journal

Eleven-year, 22-year and ~90-year solar cycles discovered in nitrate concentrations in a Dome Fuji (Antarctica) ice core [SSA]

Posted on by

http://arxiv.org/abs/2209.11330


Ice cores are known to yield information about astronomical phenomena as well as information about past climate. We report time series analyses of annually resolved nitrate variations in an ice core, drilled at the Dome Fuji station in East Antarctica, corresponding to the period from CE 1610 to 1904. Our analyses revealed clear evidence of ~11, ~22, and ~90 year periodicities, comparable to the respective periodicities of the well-known Schwabe, Hale, and Gleissberg solar cycles. Our results show for the first time that nitrate concentrations in an ice core can be used as a proxy for past solar activity on decadal to multidecadal time scales. Furthermore, 11-year and 22-year periodicities were detected in nitrate variations even during the Maunder Minimum (1645-1715), when sunspots were almost absent. This discovery may support cyclic behavior of the solar dynamo during the grand solar minimum.

Read this paper on arXiv…

Y. Motizuki, Y. Nakai, K. Takahashi, et. al.
Mon, 26 Sep 22
47/62

Comments: Submitted to Proceedings of the Japan Academy, Series B

A Seismologically Consistent Surface Rupture Length Model for Unbounded and Width-Limited Event [CL]

Posted on by

http://arxiv.org/abs/2209.10401


A new surface-rupture-length ($SRL$) relationship as a function of magnitude ($\mathbf{M}$), fault thickness, and fault dip angle is presented in this paper. The objective of this study is to model the change in scaling between unbounded and width-limited ruptures. This is achieved through the use of seismological-theory based relationships for the average displacement scaling and the aid of dynamic fault rupture simulations to constrain the rupture width scaling. The empirical dataset used in the development of this relationship is composed of $123$ events ranging from $\mathbf{M}~5$ to $8.1$ and $SRL~1.1$ to $432~km$. The dynamic rupture simulations dataset includes $554$ events ranging from $\mathbf{M}~4.9$ to $8.2$ and $SRL~1$ to $655~km$. For the average displacement ($\bar{D}$) scaling, models based on the square-root of the area ($\sqrt{A}$), on the down-dip width ($W$), and on the length ($L$) of the ruptured fault plane were evaluated. The empirical data favours a $\bar{D} \sim \sqrt{A}$ scaling. The proposed model exhibits better predictive performance compared to linear $\log(SLR)\sim\mathbf{M}$ type models, especially at the large magnitude range which dominated by width-limited events. A comparison with existing $SRL$ models shows consistent scaling at different magnitude ranges that is believed to be the result of the different magnitude ranges in the empirical dataset of the published relationships.

Read this paper on arXiv…

G. Lavrentiadis, Y. Wang, N. Abrahamson, et. al.
Thu, 22 Sep 22
48/65

Comments: 19 pages, 11 figures

Atmospheric ionization rates during a geomagnetic reversal [CL]

Posted on by

http://arxiv.org/abs/2209.10104


The Matuyama-Brunhes reversal of Earth’s magnetic dipole field took place 0.78 Ma ago, and detailed temporally resolved paleomagnetic data are available for this period. A geomagnetic reversal is expected to impact the cosmic ray flux, which in turn might impact atmospheric ionization rates. In this study a model that yields atmospheric ionization for the entire globe based on an input magnetic field is presented. Taking the time dependent paleomagnetic data as input, a 3D time series of the atmospheric ionization rates during the reversal is produced. We show, that as the dipole field weakens, the atmospheric ionization increases at low latitudes. The increase is ca. 25% at the surface and up to a factor of 5 in the upper atmosphere. Globally, ionization rates increase around 13% at the surface and up to a factor of 2 in the upper atmosphere, whereas polar regions are largely unaffected. Finally, the change in ionization due to the solar 11-year cycle is greatly affected by the reversal. The relative change in atmospheric ionization between solar-minimum and solar-maximum varies between 2 and two orders of magnitude. All atmospheric ionization data is made available for download.

Read this paper on arXiv…

J. Svensmark
Thu, 22 Sep 22
62/65

Comments: 8 Figures, 1 table

On pseudo-periodic perturbations of planetary orbits, and oscillations of Earth's rotation and revolution: Lagrange's formulation [CL]

Posted on by

http://arxiv.org/abs/2209.07213


Earth rotation is determined by polar motion (PM) and length of day (lod). The excitation sources of PM are torques linked to fluid circulations (“geophysical excitations”), and those of lod to luni-solar tides (“astronomical excitations”). We explore the links between the rotations and revolutions of planets, following Lagrange’s (1853) presentation of mechanics. The energy of a planet in motion in a central field is the sum of kinetic, centrifugal (planet dependent) and centripetal (identical for all planets) energies. For each planet, one can calculate a “constant of gravitation” Gp . For the giant planets, Gp decreases as a function of aphelia. There is no such organized behavior for the terrestrial planets. The perturbing potential of other planets generates a small angular contribution to the displacement : this happens to be identical to Einstein’s famous formula for precession. Delays in the planet’s perihelia follow a (-5/2) power law of a. This is readily understood in the Lagrange formalism (the centrifugal term takes over for small distances). The telluric planets have lost energy, probably transferred to the planets rotations. The ratio of areal velocities to rotation obeys a -5/2 power law of a. The ratio of areal velocity to integrated period R also fits a -5/2 power dependence, implying linearity of the energy exchange between revolution and rotation. For Einstein deformation of space-time by the Sun is the origin of the field perturbation. For Lagrange the perturbation could only be due to the interactions of torques. The perihelion delays, the areal velocities and the planetary rotations display power laws of aphelia, whose behavior contrasts with that of the kinetic moment. The areal velocity being linearly linked to the kinetic moment of planets, this must be the level at which the transfer is achieved.

Read this paper on arXiv…

F. Lopes, V. Courtillot, D. Gibert, et. al.
Fri, 16 Sep 22
21/84

Comments: N/A

Towards Coupling Full-disk and Active Region-based Flare Prediction for Operational Space Weather Forecasting [CL]

Posted on by

http://arxiv.org/abs/2209.07406


Solar flare prediction is a central problem in space weather forecasting and has captivated the attention of a wide spectrum of researchers due to recent advances in both remote sensing as well as machine learning and deep learning approaches. The experimental findings based on both machine and deep learning models reveal significant performance improvements for task specific datasets. Along with building models, the practice of deploying such models to production environments under operational settings is a more complex and often time-consuming process which is often not addressed directly in research settings. We present a set of new heuristic approaches to train and deploy an operational solar flare prediction system for $\geq$M1.0-class flares with two prediction modes: full-disk and active region-based. In full-disk mode, predictions are performed on full-disk line-of-sight magnetograms using deep learning models whereas in active region-based models, predictions are issued for each active region individually using multivariate time series data instances. The outputs from individual active region forecasts and full-disk predictors are combined to a final full-disk prediction result with a meta-model. We utilized an equal weighted average ensemble of two base learners’ flare probabilities as our baseline meta learner and improved the capabilities of our two base learners by training a logistic regression model. The major findings of this study are: (i) We successfully coupled two heterogeneous flare prediction models trained with different datasets and model architecture to predict a full-disk flare probability for next 24 hours, (ii) Our proposed ensembling model, i.e., logistic regression, improves on the predictive performance of two base learners and the baseline meta learner measured in terms of two widely used metrics True Skill Statistic (TSS) and Heidke Skill core (HSS), and (iii) Our result analysis suggests that the logistic regression-based ensemble (Meta-FP) improves on the full-disk model (base learner) by $\sim9\%$ in terms TSS and $\sim10\%$ in terms of HSS. Similarly, it improves on the AR-based model (base learner) by $\sim17\%$ and $\sim20\%$ in terms of TSS and HSS respectively. Finally, when compared to the baseline meta model, it improves on TSS by $\sim10\%$ and HSS by $\sim15\%$.

Read this paper on arXiv…

C. Pandey, A. Ji, R. Angryk, et. al.
Fri, 16 Sep 22
44/84

Comments: N/A

Seismic noise characterisation at Gingin high optical gravitational wave test facility [IMA]

Posted on by

http://arxiv.org/abs/2209.06559


A critical consideration in the design of next generation gravitational wave detectors is isolation from seismic vibrations that introduces various coherent and incoherent noises to the interferometers at different frequencies. We present the results of a detailed low frequency ambient seismic noise characterization (0.1–10~Hz) at Gingin High Optical Power Facility in Western Australia using a seismic array. The dominant noise sources below 1~Hz is microseism (0.06–1~Hz), strongly correlated with swell and sea heights measured by nearby buoy stations. Above 1~Hz, the seismic spectrum is dominated by wind induced seismic noise with a diurnal variation that prevents characterizing the background anthropogenic noise sources based on their daily power variations. We use f-k beamforming to distinguish between coherent and incoherent wind induced seismic noise. This allows the separation of some anthropogenic noise from wind induced noise based on the temporal variation of spatio-spectral properties. We show that the seismic coherency is reduced by wind induced seismic noise for wind speeds above 6~m/s. Furthermore, there are several spectral peaks between 4–9~Hz associated with the interaction of wind with a 40~m tall tower among which one at 4.2~Hz is strongest and coherent. By comparing our results with the properties of seismic noise at Virgo, we demonstrate that while the secondary microseism noise level is two orders of magnitude higher in Gingin (0.2~Hz), the anthropogenic noise level is three orders of magnitude lower between 2 and 4~Hz due to the absence of nearby road traffic. It is also at least one order of magnitude lower between 4 and 10~Hz due to the sparse population in Gingin.

Read this paper on arXiv…

H. Satari, C. Blair, L. Ju, et. al.
Thu, 15 Sep 22
32/67

Comments: The results have been presented at LVK conference, September 2022. 20 pages, 9 figures

Convective outgassing efficiency in planetary magma oceans: insights from computational fluid dynamics [EPA]

Posted on by

http://arxiv.org/abs/2209.06199


Planetary atmospheres are commonly thought to result from the efficient outgassing of cooling magma oceans. During this stage, vigorous convective motions in the molten interior are believed to rapidly transport the dissolved volatiles to shallow depths where they exsolve and burst at the surface. This assumption of efficient degassing and atmosphere formation has important implications for planetary evolution, but has never been tested against fluid dynamics considerations. Yet, during a convective cycle, only a finite fraction of the magma ocean can reach the shallow depths where volatiles exsolution can occur, and a large-scale circulation may prevent a substantial magma ocean volume from rapidly reaching the planetary surface. Therefore, we conducted computational fluid dynamics experiments of vigorous 2D and 3D Rayleigh-B\’enard convection at Prandtl number of unity to characterize the ability of the convecting fluid to reach shallow depths at which volatiles are exsolved and extracted to the atmosphere. Outgassing efficiency is essentially a function of the magnitude of the convective velocities. This allows deriving simple expressions to predict the time evolution of the amount of outgassed volatiles as a function of the magma ocean governing parameters. For plausible cases, the time required to exsolve all oversaturated water can exceed the magma ocean lifetime in a given highly vigorous transient stage, leading to incomplete or even negligible outgassing. Furthermore, the planet size and the initial magma ocean water content, through the convective vigor and the exsolution depth, respectively, strongly affect magma oceans degassing efficiency, possibly leading to divergent planetary evolution paths and resulting surface conditions. Overall, despite vigorous convection, for a significant range of parameters, convective degassing appears not as efficient as previously thought.

Read this paper on arXiv…

A. Salvador and H. Samuel
Wed, 14 Sep 22
65/90

Comments: 84 pages, 16 figures, 6 tables; Accepted for publication in Icarus

53Mn-53Cr chronology and ε54Cr-Δ17O genealogy of Erg Chech 002: the oldest andesite in the Solar System [EPA]

Posted on by

http://arxiv.org/abs/2209.05381


The meteorite sample Erg Chech (EC) 002 is the oldest felsic igneous rock from the Solar System analysed to date and provides a unique opportunity to study the formation of felsic crusts on differentiated protoplanets immediately after metal-silicate equilibration or core formation. The extinct 53Mn-53Cr chronometer provides chronological constraints on the formation of EC 002 by applying the isochron approach using chromite, metal-silicate-sulphide and whole-rock fractions as well as “leachates” obtained by sequential digestion of a bulk sample. Assuming a chondritic evolution of its parent body, a 53Cr/52Cr model age is also obtained from the chromite fraction. The 53Mn-53Cr isochron age of 1.73 (+/-) 0.96 Ma (anchored to D’Orbigny angirte) and the chromite model age constrained between 1.46 (-0.68/+0.78) and 2.18 (-1.06/+1.32) Ma after the formation of calcium-aluminium-rich inclusions (CAIs) agree with the 26Al-26Mg ages (anchored to CAIs) reported in previous studies. This indicates rapid cooling of EC 002 that allowed near-contemporaneous closure of multiple isotope systems. Additionally, excess in the neutron-rich 54Cr (nucleosynthetic anomalies) combined with mass-independent isotope variations of 17O provide genealogical constraints on the accretion region of the EC 002 parent body. The 54Cr and 17O isotope compositions of EC 002 confirm its origin in the “non-carbonaceous” reservoir and overlap with the vestoid material NWA 12217 and anomalous eucrite EET 92023. This indicates a common feeding zone during accretion in the protoplanetary disk between the source of EC 002 and vestoids. The enigmatic origin of iron meteorites remains still unresolved as EC 002, which is more like a differentiated crust, has an isotope composition that does not match known irons meteorite groups that were once planetesimal cores.

Read this paper on arXiv…

A. Anand, P. Kruttasch and K. Mezger
Tue, 13 Sep 22
24/85

Comments: Accepted in ‘Meteoritics & Planetary Science’ journal

The Oscillatory Motion of Jupiter's Polar Cyclones Results From Vorticity Dynamics [EPA]

Posted on by

http://arxiv.org/abs/2209.00309


The polar cyclone at Jupiter’s south pole and the five cyclones surrounding it oscillate in position and interact. These cyclones, observed since 2016 by NASA’s Juno mission, present a unique opportunity to study vortex dynamics and interactions on long time scales. The cyclones’ position data, acquired by Juno’s JIRAM instrument, is analyzed, showing dominant oscillations with ~12 month periods and amplitudes of ~400 km. Here, the mechanism driving these oscillations is revealed by considering vorticity-gradient forces generated by mutual interactions between the cyclones and the latitudinal variation in planetary vorticity. Data-driven estimation of these forces exhibits a high correlation with the measured acceleration of the cyclones. To further test this mechanism, a model is constructed, simulating how cyclones subject to these forces exhibit similar oscillatory motion.

Read this paper on arXiv…

N. Gavriel and Y. Kaspi
Fri, 2 Sep 22
60/62

Comments: 9 pages, 5 figures, 11 supplementary pages, 9 supplementary figures

Effect of projectile shape and interior structure on crater size in strength regime [EPA]

Posted on by

http://arxiv.org/abs/2208.11568


Experiments on crater formation in the strength regime were conducted using projectiles of various shapes with an aspect ratio of ~1, including both solid and hollow interiors. The surface diameter, inner (pit) diameter, and depth of the craters on basalt and porous gypsum targets were measured. Using the bulk density of the projectile, the surface diameter and depth for basalt and the pit diameter and depth for porous gypsum were scaled using the pi-scaling law for crater formation in the strength regime. The numerical code iSALE was used to simulate the impact of projectiles of various shapes and interior structure with similar bulk densities. Results show that the distributions of the maximum (peak) pressure experienced and particle velocity in the targets were similar regardless of projectile shape and interior structure, implying that the dimensions of the final craters were almost identical. This is consistent with the experimental results. Thus, we conclude that the size of the craters formed by the impact of projectiles with different shape and interior structure can be scaled using a conventional scaling law in the strength regime, using bulk density as projectile density.

Read this paper on arXiv…

T. Kadono, M. Arakawa, S. Tsujido, et. al.
Thu, 25 Aug 22
27/43

Comments: 38 pages, 9 figures, 4 tables, 1 supporting information, accepted for publication in Earth, Planets and Space

Insight into the Distribution of High-pressure Shock Metamorphism in Rubble-pile Asteroids [EPA]

Posted on by

http://arxiv.org/abs/2208.11006


Shock metamorphism in ordinary chondrites allows for reconstructing impact events between asteroids in the main asteroid belt. Shock-darkening of ordinary chondrites occurs at the onset of complete shock melting of the rock (>70 GPa) or injection of sulfide and metal melt into the cracks within solid silicates (\sim 50 GPa). Darkening of ordinary chondrites masks diagnostic silicate features observed in the reflectance spectrum of S-complex asteroids so they appear similar to C/X-complex asteroids. In this work, we investigate the shock pressure and associated metamorphism pattern in rubble-pile asteroids at impact velocities of 4-10 km/s. We use the iSALE shock physics code and implement two-dimensional models with simplified properties in order to quantify the influence of the following parameters on shock-darkening efficiency: impact velocity, porosity within the asteroid, impactor size, and ejection efficiency. We observe that, in rubble-pile asteroids, the velocity and size of the impactor are the constraining parameters in recording high-grade shock metamorphism. Yet, the recorded fraction of higher shock stages remains low (<0.2). Varying the porosity of the boulders from 10% to 30% does not significantly affect the distribution of pressure and fraction of shock-darkened material. The pressure distribution in rubble-pile asteroids is very similar to that of monolithic asteroids with the same porosity. Thus, producing significant volumes of high-degree shocked ordinary chondrites requires strong collision events (impact velocities above 8 km/s and/or large sizes of impactors). A large amount of asteroid material escapes during an impact event (up to 90%); however, only a small portion of the escaping material is shock-darkened (6%).

Read this paper on arXiv…

N. Güldemeister, J. Moreau, T. Kohout, et. al.
Wed, 24 Aug 22
36/67

Comments: 12 pages, 9 figures

VapoRock: Thermodynamics of vaporized silicate melts for modeling volcanic outgassing and magma ocean atmospheres [EPA]

Posted on by

http://arxiv.org/abs/2208.09582


Silicate vapors play a key role in planetary evolution, especially dominating early stages of rocky planet formation through outgassed magma ocean atmospheres. Our open-source thermodynamic modeling software “VapoRock” combines the MELTS liquid model (Ghiorso et al. 1995) with gas-species properties from multiple thermochemistry tables (e.g. Chase et al. 1998). VapoRock calculates abundances of 34 gaseous species in equilibrium with magmatic liquid in the system Si-Mg-Fe-Al-Ca-Na-K-Ti-Cr-O at desired temperatures and oxygen fugacities (fO2, or partial pressure of O2). Comparison with experiments shows that pressures and melt-oxide activities (which vary over many orders of magnitude) are reproduced within a factor of ~3, consistent with measurement uncertainties. We also benchmark against a wide selection of igneous rock compositions including bulk silicate Earth, predicting elemental vapor abundances that are comparable (Na, Ca, & Al) or more realistic (K, Si, Mg, Fe, & Ti) than those of the closed-source MAGMA code (with maximum deviations by factors of 30-300 for K). Calculated vapor abundances depend critically on liquid activities, and the MELTS model underpinning VapoRock was specifically calibrated on natural igneous liquids and has been extensively tested & refined over the last 3 decades. In contrast, MAGMA’s underlying liquid model assumes ideal mixtures of liquid pseudo-species, which are incapable of capturing the non-ideal compositional interactions that typify the behavior of natural silicate melts. Using VapoRock, we finally explore how relative abundances of SiO and SiO2 provide a spectroscopically measurable proxy for oxygen fugacity in devolatilized exoplanetary atmospheres, potentially constraining fO2 in outgassed exoplanetary mantles.

Read this paper on arXiv…

A. Wolf, N. Jäggi, P. Sossi, et. al.
Tue, 23 Aug 22
6/79

Comments: N/A

Time scales of small body differentiation [EPA]

Posted on by

http://arxiv.org/abs/2208.10357


The petrologic and geochemical diversity of meteorites is a function of the bulk composition of their parent bodies, but also the result of how and when internal differentiation took place. Here we focus on this second aspect considering the two principal parameters involved: size and accretion time of the body. We discuss the interplay of the various time scales related to heating, cooling and drainage of silicate liquids. Based on two phase flow modelling in 1-D spherical geometry, we show that drainage time is proportional to two independent parameters: $\mu_m/R^2$, the ratio of the matrix viscosity to the square of the body radius and $\mu_f/a^2$, the ratio of the liquid viscosity to the square of the matrix grain size. We review the dependence of these properties on temperature, thermal history and degree of melting, demonstrating that they vary by several orders of magnitude during thermal evolution. These variations call into question the results of two phase flow modelling of small body differentiation that assume constant properties.For example, the idea that liquid migration was efficient enough to remove $^{26}$Al heat sources from the interior of bodies and dampen their melting (e.g. Moskovitz and Gaidos, 2011; Neumann et al., 2012) relies on percolation rates of silicate liquids overestimated by six to eight orders of magnitude. In bodies accreted during the first few million years of solar-system history, we conclude that drainage cannot prevent the occurrence of a global magma ocean. These conditions seem ideal to explain the generation of the parent-bodies of iron meteorites. A map of the different evolutionary scenarios of small bodies as a function of size and accretion time is proposed.

Read this paper on arXiv…

M. Monnereau, J. Guignard, A. Néri, et. al.
Tue, 23 Aug 22
73/79

Comments: 18 pages, 9 figures, Submitted to Icarus on August 9th 2022

The planetary theory of solar activity variability: a review [CL]

Posted on by

http://arxiv.org/abs/2208.09293


Commenting the 11-year sunspot cycle, Wolf (1859, MNRAS 19, 85-86) conjectured that “the variations of spot frequency depend on the influences of Venus, Earth, Jupiter, and Saturn”. The high synchronization of our planetary system is already nicely revealed by the fact that the ratios of the planetary orbital radii are closely related to each other through a scaling-mirror symmetry equation (Bank and Scafetta, Front. Astron. Space Sci. 8, 758184, 2022). Reviewing the many planetary harmonics and the orbital invariant inequalities that characterize the planetary motions of the solar system from the monthly to the millennial time scales, we show that they are not randomly distributed but clearly tend to cluster around some specific values that also match those of the main solar activity cycles. In some cases, planetary models have even been able to predict the time-phase of the solar oscillations including the Schwabe 11-year sunspot cycle. We also stress that solar models based on the hypothesis that solar activity is regulated by its internal dynamics alone have never been able to reproduce the variety of the observed cycles. Although planetary tidal forces are weak, we review a number of mechanisms that could explain how the solar structure and the solar dynamo could get tuned to the planetary motions. In particular, we discuss how the effects of the weak tidal forces could be significantly amplified in the solar core by an induced increase in the H-burning. Mechanisms modulating the electromagnetic and gravitational large-scale structure of the planetary system are also discussed.

Read this paper on arXiv…

N. Scafetta and A. Bianchini
Mon, 22 Aug 22
10/53

Comments: 33 pages, 9 figures, 7 tables

Overcoming 1 part in $10^9$ of Earth angular rotation rate measurement with the G Wettzell data [CL]

Posted on by

http://arxiv.org/abs/2208.09134


The absolute measurement of the Earth angular rotation rate with ground-based instruments becomes challenging if the 1 part in $10^9$ of precision has to be obtained. This threshold is important for fundamental physics and for geodesy, to investigate effects of General Relativity and Lorentz violation in the gravity sector and to provide the fast variation of the Earth rotation rate.
High sensitivity Ring Laser Gyroscopes (RLG) are currently the only promising technique to achieve this task in the near future, but their precision has been so far limited by systematics related to the laser operation.
In this paper we analyze two different sets of observations, each of them three days long. They were obtained from the G ring laser at the Geodetic Observatory Wettzell. The applied method has been developed for the GINGERINO ring laser in order to identify and extract the laser systematics. For the available data sets the residuals show mostly white noise behavior and the Allan deviation drops below 1 part in $10^9$ after an integration time of about $10^4$~s.

Read this paper on arXiv…

A. Virgilio, G. Terreni, A. Basti, et. al.
Mon, 22 Aug 22
38/53

Comments: 10 pages, 6 figures

Linking Common Multispectral Vegetation Indices to Hyperspectral Mixture Models: Results from 5 nm, 3 m Airborne Imaging Spectroscopy in a Diverse Agricultural Landscape [CL]

Posted on by

http://arxiv.org/abs/2208.06480


For decades, agronomists have used remote sensing to monitor key crop parameters like biomass, fractional cover, and plant health. Vegetation indices (VIs) are popular for this purpose, primarily leveraging the spectral red edge in multispectral imagery. In contrast, spectral mixture models use the full reflectance spectrum to simultaneously estimate area fractions of multiple endmember materials present within a mixed pixel. Here, we characterize the relationships between hyperspectral endmember fractions and 6 common multispectral VIs in crops & soils of California agriculture. Fractional area of green vegetation (Fv) was estimated directly from 64,000,000 5 nm, 3 to 5 m reflectance spectra compiled from a mosaic of 15 AVIRIS-ng flightlines. Simulated Planet SuperDove reflectance spectra were then derived from the AVIRIS-ng, and used to compute 6 popular VIs (NDVI, NIRv, EVI, EVI2, SR, DVI). Multispectral VIs were compared to hyperspectral Fv using parametric (Pearson correlation, r) and nonparametric (Mutual Information, MI) similarity metrics. 4 VIs (NIRv, DVI, EVI, EVI2) showed strong linear relationships to Fv (r > 0.94; MI > 1.2). NIRv & DVI showed strong interrelation (r > 0.99, MI > 2.4), but deviated significantly from 1:1 relative to Fv. EVI & EVI2 were also strongly interrelated (r > 0.99, MI > 2.3) and more closely followed a 1:1 relation with Fv. In contrast, NDVI & SR showed weaker, nonlinear, heteroskedastic relation to Fv (r < 0.84, MI = 0.69). NDVI showed especially severe sensitivity to substrate background reflectance (-0.05 < NDVI < +0.6 for unvegetated spectra) and saturation (0.2 < Fv < 0.8 for NDVI = 0.7). These direct observational constraints on multispectral VI and hyperspectral mixture model comparability can serve as a quantitative benchmark for agronomic applications in the coming era of increasing spatial & spectral resolution Earth observation.

Read this paper on arXiv…

D. Sousa and C. Small
Tue, 16 Aug 22
44/74

Comments: 18 pages

Impact of climate change on site characteristics of eight major astronomical observatories using high-resolution global climate projections until 2050 [IMA]

Posted on by

http://arxiv.org/abs/2208.04918


Sites for next-generation telescopes are chosen decades before the first light of a telescope. Site selection is usually based on recent measurements over a period that is too short to account for long-term changes in observing conditions such as those arising from anthropogenic climate change. In this study, we analyse trends in astronomical observing conditions for eight sites. Most sites either already host telescopes that provide in situ measurements of weather parameters or are candidates for hosting next-generation telescopes. For a fine representation of orography, we use the highest resolution global climate model (GCM) ensemble available provided by the high-resolution model intercomparison project and developed as part of the European Union Horizon 2020 PRIMAVERA project. We evaluate atmosphere-only and coupled PRIMAVERA GCM historical simulations against in situ measurements and the fifth generation atmospheric reanalysis (ERA5) of the ECMWF. The projections of changes in current site conditions are then analysed for the period 2015-2050 using PRIMAVERA future climate simulations. Over most sites, we find that PRIMAVERA GCMs show good agreement in temperature, specific humidity, and precipitable water vapour compared to in situ observations and ERA5. The ability of PRIMAVERA to simulate those variables increases confidence in their projections. For those variables, the model ensemble projects an increasing trend for all sites. On the other hand, no significant trends are projected for relative humidity, cloud cover, or astronomical seeing and PRIMAVERA does not simulate these variables well compared to observations and reanalyses. Therefore, there is little confidence in these projections. Our results show that climate change likely increases time lost due to bad site conditions.

Read this paper on arXiv…

C. Haslebacher, M. Demory, B. Demory, et. al.
Wed, 10 Aug 22
64/66

Comments: 53 pages, 35 figures. accepted for publication in A&A

The Resonant Tidal Evolution of the Earth-Moon Distance [EPA]

Posted on by

http://arxiv.org/abs/2207.00438


Due to tidal interactions in the Earth-Moon system, the spin of the Earth slows down and the Moon drifts away. This recession of the Moon is now measured with great precision, but it has been realized, more than fifty years ago, that simple tidal models extrapolated back in time lead to an age of the Moon that is by far incompatible with the geochronological and geochemical evidence. In order to evade this problem, more elaborate models have been proposed, taking into account the oceanic tidal dissipation. However, these models did not fit both the estimated lunar age and the present rate of lunar recession simultaneously. Here we present a physical model that reconciles these two constraints and yields a unique solution of the tidal history. This solution fits well the available geological proxies for the history of the Earth-Moon system and consolidates the cyclostratigraphic method. The resulting evolution involves multiple crossings of resonances in the oceanic dissipation that are associated with significant and rapid variations in the lunar orbital distance, the Earth’s length of the day, and the Earth’s obliquity.

Read this paper on arXiv…

M. Farhat, P. Auclair-Desrotour, G. Boué, et. al.
Mon, 4 Jul 22
42/62

Comments: N/A

Seismology in the Solar System [EPA]

Posted on by

http://arxiv.org/abs/2206.01785


The NASA InSight mission has helped to measure the deep interior of Mars using observations of seismic waves excited by marsquakes. Currently, installation of seismometers on the moon is foreseen. We review the case for seismic experiments on all major planetary bodies of the solar system. We discuss scientific goals in accordance with the Decadal survey for planetary science and astrobiology and the ESA Voyage 2050 program as well as technical challenges and potential mission concepts, to answer the question: Where could we do seismology on other planets and why should we do it?

Read this paper on arXiv…

S. Stähler and M. Knapmeyer
Tue, 7 Jun 22
21/70

Comments: 36 pages, 15 figures, in press for Advances in Geophysics, vol. 63

Conservation of Total Wave Action in the Expanding Solar Wind [SSA]

Posted on by

http://arxiv.org/abs/2206.01809


The conservation of wave action in moving plasmas has been well-known for over half a century. However, wave action is not conserved when multiple wave modes propagate and coexist close to degeneration condition (Sound speed equals Alfv\’en speed, i.e. plasma $\beta \sim 1$). Here we show that the violation of conservation is due to wave mode conversion, and that the total wave action summed over interacting modes is still conserved. Though the result is general, we focus on MHD waves and identify three distinctive mode conversion mechanisms, i.e. degeneracy, linear mode conversion, and resonance, and provide an intuitive physical picture for the mode conversion processes. We use 1D MHD simulations with the Expanding Box Model to simulate the nonlinear evolution of monochromatic MHD waves in the expanding solar wind. Simulation results validate the theory; total wave action therefore remains an interesting diagnostic for studies of waves and turbulence in the solar wind.

Read this paper on arXiv…

Z. Huang, C. Shi, M. Velli, et. al.
Tue, 7 Jun 22
39/70

Comments: Accepted by ApJ

Changing spatial distribution of water flow charts major change in Mars' greenhouse effect [EPA]

Posted on by

http://arxiv.org/abs/2206.00036


Early Mars had rivers, but the cause of Mars’ wet-to-dry transition remains unknown. Past climate on Mars can be probed using the spatial distribution of climate-sensitive landforms. We analyzed global databases of water-worked landforms and identified changes in the spatial distribution of rivers over time. These changes are simply explained by comparison to a simplified meltwater model driven by an ensemble of global climate model simulations, as the result of $\gtrsim$10 K global cooling, from global average surface temperature (T) $\ge$ 268 K to T $\sim$ 258 K, due to a weaker greenhouse effect. In other words, river-forming climates on Early Mars were warm and wet first, and cold and wet later. Surprisingly, analysis of the greenhouse effect within our ensemble of global climate model simulations suggests that this shift was primarily driven by waning non-CO2 radiative forcing, and not changes in CO2 radiative forcing.

Read this paper on arXiv…

E. Kite, M. Mischna, B. Fan, et. al.
Thu, 2 Jun 22
37/57

Comments: N/A

Water storage capacity of the Martian mantle through time [CL]

Posted on by

http://arxiv.org/abs/2205.15450


Water has been stored in the Martian mantle since its formation, primarily in nominally anhydrous minerals. The short-lived early hydrosphere and intermittently flowing water on the Martian surface may have been supplied and replenished by magmatic degassing of water from the mantle. Estimating the water storage capacity of the solid Martian mantle places important constraints on its water inventory and helps elucidate the sources, sinks, and temporal variations of water on Mars. In this study, we applied a bootstrap aggregation method to investigate the effects of iron on water storage capacities in olivine, wadsleyite, and ringwoodite, based on high-pressure experimental data compiled from the literature, and we provide a quantitative estimate of the upper bound of the bulk water storage capacity in the FeO-rich solid Martian mantle. Along a series of areotherms at different mantle potential temperatures ($T_{p}$), we estimated a water storage capacity equal to $9.0_{-2.2} ^{+2.8}$ km Global Equivalent Layer (GEL) for the present-day Martian mantle at $T_{p}$ = 1600 K and $4.9_{-1.5}^{+1.7}$ km GEL for the initial Martian mantle at $T_{p}$ = 1900 K. The water storage capacity of the Martian mantle increases with secular cooling through time, but due to the lack of an efficient water recycling mechanism on Mars, its actual mantle water content may be significantly lower than its water storage capacity today.

Read this paper on arXiv…

J. Dong, R. Fischer, L. Stixrude, et. al.
Wed, 1 Jun 22
21/65

Comments: 52 pages including supplementary materials, 14 figures, 13 tables; manuscript accepted for publication in Icarus

Shock recovery with decaying compressive pulses: Shock effects in calcite (CaCO$_3$) around the Hugoniot elastic limit [EPA]

Posted on by

http://arxiv.org/abs/2205.09385


Shock metamorphism of minerals in meteorites provides insights into the ancient Solar System. Calcite is an abundant aqueous alteration mineral in carbonaceous chondrites. Return samples from the asteroids Ryugu and Bennu are expected to contain calcite-group minerals. Although shock metamorphism in silicates has been well studied, such data for aqueous alteration minerals are limited. Here, we investigated the shock effects in calcite with marble using impact experiments at the Planetary Exploration Research Center of Chiba Institute of Technology. We produced decaying compressive pulses with a smaller projectile than the target. A metal container facilitates recovery of a sample that retains its pre-impact stratigraphy. We estimated the peak pressure distributions in the samples with the iSALE shock physics code. The capability of this method to produce shocked grains that have experienced different degrees of metamorphism from a single experiment is an advantage over conventional uniaxial shock recovery experiments. The shocked samples were investigated by polarizing microscopy and X-ray diffraction analysis. We found that more than half of calcite grains exhibit undulatory extinction when peak pressure exceeds 3 GPa. This shock pressure is one order of magnitude higher than the Hugoniot elastic limit (HEL) of marble, but it is close to the HEL of a calcite crystal, suggesting that the undulatory extinction records dislocation-induced plastic deformation in the crystal. Finally, we propose a strategy to re-construct the maximum depth of calcite grains in a meteorite parent body, if shocked calcite grains are identified in chondrites and/or return samples from Ryugu and Bennu.

Read this paper on arXiv…

K. Kurosawa, H. Ono, T. Niihara, et. al.
Fri, 20 May 22
13/65

Comments: 25 pages, 9 figures, 1 table, 1 supporting information, accepted for publication in Journal of Geophysical Research Planets

The specific heat of astro-materials: Review of theoretical concepts, materials and techniques [EPA]

Posted on by

http://arxiv.org/abs/2205.08212


We provide detailed background, theoretical and practical, on the specific heat cp of minerals and mixtures thereof, ‘astro-materials’, as well as background information on common minerals and other relevant solid substances found on the surfaces of solar system bodies. Furthermore, we demonstrate how to use specific heat and composition data for lunar samples and meteorites as well as a new database of endmember mineral heat capacities (the result of an extensive literature review) to construct reference models for the isobaric specific heat cP as a function of temperature for common solar system materials. Using a (generally linear) mixing model for the specific heat of minerals allows extrapolation of the available data to very low and very high temperatures, such that models cover the temperature range between 10 and 1000 K at least (and pressures from zero up to several kbars). We describe a procedure to estimate cp(T) for virtually any solid solar system material with a known mineral composition, e.g., model specific heat as a function of temperature for a number of typical meteorite classes with known mineralogical compositions. We present, as examples, the cp(T) curves of a number of well-described laboratory regolith analogues, as well as for planetary ices and ‘tholins’ in the outer solar system. Part II will review and present the heat capacity database for minerals and compounds and part III is going to cover applications, standard reference compositions, cp(T) curves and a comparison with new and literature experimental data.

Read this paper on arXiv…

J. Biele, M. Grott, M. Zolensky, et. al.
Wed, 18 May 22
65/66

Comments: submitted to Special Issue for International Journal of Thermophysics ‘Thermophysics of Advanced Spacecraft Materials and Extraterrestrial Samples’ Part II to be submitted still in 2022

The Effect of Ocean Salinity on Climate and Its Implications for Earth's Habitability [EPA]

Posted on by

http://arxiv.org/abs/2205.06785


The influence of atmospheric composition on the climates of present-day and early Earth has been studied extensively, but the role of ocean composition has received less attention. We use the ROCKE-3D ocean-atmosphere general circulation model to investigate the response of Earth’s present-day and Archean climate system to low vs. high ocean salinity. We find that saltier oceans yield warmer climates in large part due to changes in ocean dynamics. Increasing ocean salinity from 20 g/kg to 50 g/kg results in a 71% reduction in sea ice cover in our present-day Earth scenario. This same salinity change also halves the pCO$_2$ threshold at which Snowball glaciation occurs in our Archean scenarios. In combination with higher levels of greenhouse gases such as CO$_2$ and CH$_4$, a saltier ocean may allow for a warm Archean Earth with only seasonal ice at the poles despite receiving 20% less energy from the Sun.

Read this paper on arXiv…

S. Olson, M. Jansen, D. Abbot, et. al.
Mon, 16 May 22
31/42

Comments: Accepted for publication in Geophysical Research Letters 04/19/22