http://arxiv.org/abs/1903.07205
Lunar laser ranging (LLR) data and Apollo seismic data analyses, revealed independent evidence for the presence of a fluid lunar core. However, the size of the lunar fluid core remained uncertain by $\pm 40$ km. Here we show that a new description of the lunar interior’s dynamical model provides a determination of the radius and geometry of the lunar core-mantle boundary (CMB) from the LLR observations. We compare the present-day lunar core oblateness obtained from LLR analysis with the expected hydrostatic model values, over a range of previously expected CMB radii. The findings suggest a core oblateness ($f_c=(2.13 \pm 0.53) \times 10^{-4}$) that satisfies the assumption of hydrostatic equilibrium over a tight range of lunar CMB radii ($\mathcal{R}_{CMB} \approx 384 \pm 12$ km). Our estimates of a presently-relaxed lunar CMB translates to a core mass fraction in the range of $1.63-2.06\%$ with a present-day Free Core Nutation (FCN) within $(374 \pm 93)$ years. In addition, a better constraint on the lunar CMB radii translates to an improvement on the precision tests of fundamental physics using LLR data. Our methods can also be applied to study the influence of the liquid core on the rotation of other planets, especially Mars, with the recent advent of the InSight mission.
V. Viswanathan, N. Rambaux, A. Fienga, et. al.
Tue, 19 Mar 19
6/100
Comments: Submitted for publication in Geophysical Research Letters
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