Tidal pull of the Earth strips the proto-Moon of its volatiles

Status Report From: e-Print archive
Posted: Tuesday, May 4, 2021

S. Charnoz, P.A. Sossi, Y-N Lee, J. Siebert, R. Hyodo, L. Allibert, F.C. Pignatale, M. Landeau, A.V. Oza, F. Moynier

Prevailing models for the formation of the Moon invoke a giant impact between a planetary embryo and the proto-Earth \citep{Canup_2004, Cuk_Stewart_2012}. Despite similarities in the isotopic and chemical abundances of refractory elements compared to Earth's mantle, the Moon is depleted in volatiles \citep{Wolf_Anders_1980}. Current models favour devolatilisation via incomplete condensation of the proto-Moon in an Earth-Moon debris-disk \citep{Charnoz_Michaut_2015,Canup_2015,Lock_2018}. However the physics of this protolunar disk is poorly understood and thermal escape of gas is inhibited by the Earth's strong gravitational field \citep{Nakajima_Stevenson_2014}. Here we investigate a simple process, wherein the Earth's tidal pull promotes intense hydrodynamic escape from the liquid surface of a molten proto-Moon assembling at 3-6 Earth radii. Such tidally-driven atmospheric escape persisting for less than 1 Kyr at temperatures ∼1600−1700 K reproduces the measured lunar depletion in K and Na.

Comments: Accepted for publication in ICARUS

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Cite as: arXiv:2105.00917 [astro-ph.EP] (or arXiv:2105.00917v1 [astro-ph.EP] for this version)

Submission history

From: Sebastien Charnoz 

[v1] Fri, 30 Apr 2021 10:00:47 UTC (12,339 KB)

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