Determining the source(s) of water in the lunar interior

Barnes, J. J.; Tartèse, R.; Anand, M.; Franchi, I. A.; Russell, S. S. and Kring, D. A. (2015). Determining the source(s) of water in the lunar interior. In: 46th Lunar and Planetary Science Conference, article no. 2159.



Recently, there have been numerous studies investigating the amount and isotopic composition of water in lunar materials. The combined results from these investigations have provided two major insights that have challenged the long-standing paradigm of an anhydrous Moon. The first major insight relates to the new estimates for the water content of the bulk silicate Moon (BSM) ranging from ~ 10 to ~ 400 ppm H2O. The second major insight is related to the source of lunar water, which ranges from Oort cloud comets, to carbonaceous chondrite-like asteroids, or perhaps even from the proto-Earth. Whilst we have some understanding about the flux of asteroids and comets to the Moon during the purported ‘late heavy bombardment’ (LHB; ~ 10 % comets, 90 % asteroids), we have very limited understanding of the flux of these objects during the first ~ 100 Ma of lunar history (i.e., during lunar differentiation or lunar magma ocean (LMO) stage).

In this study, we have estimated the mass of water delivered to the Moon in the first 100 Ma of its geological history that satisfies current estimates of water in the BSM, followed by an estimate of the relative proportions of asteroidal and cometary material delivered to the Moon that is consistent with the H-isotopic composition of water in the lunar interior.

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