The composition of Solar system asteroids and Earth/Mars moons, and the Earth-Moon composition similarity

Status Report From: e-Print archive
Posted: Thursday, April 20, 2017

Alessandra Mastrobuono-Battisti, Hagai B. Perets
(Submitted on 17 Apr 2017)

[abridged] In the typical giant-impact scenario for the Moon formation most of the Moon's material originates from the impactor. Any Earth-impactor composition difference should, therefore, correspond to a comparable Earth-Moon composition difference. Analysis of Moon rocks shows a close Earth-Moon composition similarity, posing a challenge for the giant-impact scenario, given that impactors were thought to significantly differ in composition from the planets they impact. Here we use a large set of 140 simulations to show that the composition of impactors could be very similar to that of the planets they impact; in 4.9%-18.2% (1.9%-6.7%) of the cases the resulting composition of the Moon is consistent with the observations of Δ17O<15 (Δ17O<6 ppm). These findings suggest that the Earth-Moon composition similarity could be resolved as to arise from the primordial Earth-impactor composition similarity. Note that although we find the likelihood for the suggested competing model of very high mass-ratio impacts (producing significant Earth-impactor composition mixing) is comparable (<6.7%), this scenario also requires additional fine-tuned requirements of a very fast spinning Earth. Using the same simulations we also explore the composition of giant-impact formed Mars-moons as well as Vesta-like asteroids. We find that the Mars-moon composition difference should be large, but smaller than expected if the moons are captured asteroids. Finally, we find that the left-over planetesimals ('asteroids') in our simulations are frequently scattered far away from their initial positions, thus potentially explaining the mismatch between the current position and composition of the Vesta asteroid.

Comments:    15 pages, 12 figures, resubmitted to MNRAS after referee comments. Abstract abridged for arXiv submission
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:    arXiv:1704.05082 [astro-ph.EP] (or arXiv:1704.05082v1 [astro-ph.EP] for this version)
Submission history
From: Alessandra Mastrobuono Battisti 
[v1] Mon, 17 Apr 2017 18:14:01 GMT (5306kb)

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