Water in the Moon's interior: Truth and consequences

By E. Hauri, A. Saal, M. Rutherford, J. Orman. 2015

237 citations recorded by the source corpus.

Abstract Geochemical data for H 2 O and other volatiles, as well as major and trace elements, are reported for 377 samples of lunar volcanic glass from three chemical groups (A15 green, A15 yellow, A17 orange 74 220). These data demonstrate that degassing is a pervasive process that has affected all extrusive lunar rocks. The data are combined with published data to estimate the total composition of the bulk silicate Moon (BSM). The estimated BSM composition for highly volatile elements, constrained by H 2 O/Ce ratios and S contents in melt inclusions from orange glass sample 74 220, are only moderately depleted compared with the bulk silicate Earth (avg. 0.25X BSE) and essentially overlap the composition of the terrestrial depleted MORB source. In a single giant impact origin for the Moon, the Moon-forming material experiences three stages of evolution characterized by very different timescales. Impact mass ejection and proto-lunar disk evolution both permit system loss of H 2 O and other volatiles on timescales ranging from days to centuries; the early Moon is likely to have accreted from a thin magma disk of limited volume embedded in, but largely displaced from, the extended distribution of vapor around the Earth. Only the protracted evolution of the lunar magma ocean (LMO) presents a time window sufficiently long (10–200 Ma) for the Moon to gain water during the tail end of accretion. This “hot start” to lunar formation is however not the only model that matches the lunar volatile abundances; a “cold start” in which the proto-lunar disk is largely composed of solid material could result in efficient delivery of terrestrial water to the Moon, while a “warm start” producing a disk of 25% volatile-retentive solids and 75% volatile-depleted magma/vapor is also consistent with the data. At the same time, there exists little evidence that the Moon formed in a singular event, as all detailed planetary accretion models predict several giant impacts in the terrestrial planet region in which the Earth forms. It is thus conceivable that the Moon, like the Earth, experienced a history of heterogeneous accretion.

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/165a06d55a307f7df7c9c4dc5ae311a104462dca

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Citations in the corpus

Generation, ascent and eruption of magma on the Moon:new insights into source depths, magma supply, intrusions and effusive/explosive eruptions (Part 2: Predicted Emplacement Processes and Observations) (2017, methodology): “In earlier treatments ( Wilson and Head, 1981 ; Head and Wilson, 1992a ; Fogel and Rutherford, 1995 ) it was assumed that n was a few to several hundred ppm, but recent work suggests values up to at last a few thousand ppm ( Saal et al., 2008; Hauri et al., 2011, 2015; Wetzel et al., 2015 ).”
The timeline of the lunar bombardment: Revisited (2018, background): “2000-3000 ppm) than for Earth’s mantle and is also significantly higher than the low sulfur concentration of ∼ 75 ppm that has been estimated for the lunar mantle (Chen et al., 2015; Hauri et al., 2015; McCubbin et al., 2015).”