Lin Yanhao, van Westrenen Wim
Department of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam 1081 HV, The Netherlands.
Natl Sci Rev. 2019 Nov;6(6):1247-1254. doi: 10.1093/nsr/nwz033. Epub 2019 Mar 11.
The traditional view of a dry, volatile-poor Moon has been challenged by the identification of water and other volatiles in lunar samples, but the volatile budget delivery time(s), source(s) and temporal evolution remain poorly constrained. Here we show that hydrogen and chlorine isotopic ratios in lunar apatite changed significantly during the Late Accretion (LA, 4.1-3.8 billion years ago). During this period, deuterium/hydrogen ratios in the Moon changed from initial carbonaceous-chondrite-like values to values consistent with an influx of ordinary-chondrite-like material and pre-LA elevated δCl values drop towards lower chondrite-like values. Inferred pre-LA lunar interior water contents are significantly lower than pristine values suggesting degassing, followed by an increase during the LA. These trends are consistent with dynamic models of solar-system evolution, suggesting that the Moon's (and Earth's) initial volatiles were replenished ∼0.5 Ga after their formation, with their final budgets reflecting a mixture of sources and delivery times.
月球样本中发现水和其他挥发性物质，这对传统观点中干燥且挥发性物质匮乏的月球提出了挑战，但挥发性物质的预算输送时间、来源及时间演化仍受到很大限制。我们在此表明，月球磷灰石中的氢和氯同位素比率在晚期吸积阶段（LA，41亿至38亿年前）发生了显著变化。在此期间，月球的氘/氢比率从最初类似碳质球粒陨石的值变为与类似普通球粒陨石物质的流入相一致的值，且吸积前升高的δCl值向更低的类似球粒陨石的值下降。推断的吸积前月球内部水含量显著低于原始值，表明发生了脱气作用，随后在晚期吸积阶段有所增加。这些趋势与太阳系演化的动力学模型一致，表明月球（以及地球）的初始挥发性物质在形成后约0.5 Ga得到了补充，其最终预算反映了多种来源和输送时间的混合情况。
