Martian water ice clouds during the 2018 global dust event as observed by the ACS-MIR channel onboard the Trace Gas Orbiter [EPA]

http://arxiv.org/abs/1912.08018


The Atmospheric Chemistry Suite (ACS) instrument onboard the ExoMars Trace Gas Orbiter (TGO) ESA-Roscosmos mission began science operations in March 2018. Here we use the solar occultation IR observations in the 2.3 — 4.2~$\mu$m spectral range, of the Mid InfraRed (MIR) channel, to monitor the behavior of the Martian water ice clouds before and during the MY 34 Global Dust Event (GDE) with a temporal coverage from $L_s=165^\circ$ to $L_s=243^\circ$. During this period, we observe water ice clouds with effective radii from 0.1~$\mu$m to an upper limit of 2~$\mu$m given by our method. Altitudes reach maximum values of about 60~km before the GDE, and up to above 90~km during the event, with more frequent high altitude values compared to non-GDE years at the same season. Particle size frequently decreases with altitude, both locally within a given profile and globally in the whole dataset. The maximum altitude at which a given size is observed can increases during the GDE by several tens of km for certain sizes. We notably notice some large water ice particles ($r_\mathrm{eff}\geq1.5~\mu$m) at surprisingly high altitudes during the GDE (50 — 70 km). This result suggest that a GDE can significantly impact the formation and properties of high altitude water ice clouds as compared to the usual perihelion dust activity.

Read this paper on arXiv…

A. Stcherbinine, M. Vincendon, F. Montmessin, et. al.
Wed, 18 Dec 19
2/71

Comments: Submitted to JGR: Planets (25 pages, 17 figures, 2 tables)