Investigating the Distribution and Source(s) of Lunar Volatiles

Following the renewed interest in the volatile inventory of the Moon witnessed in the last decade, from both sample studies and data from orbital missions, it is timely to reassess the distribution and likely source(s) of light element volatiles (C, N, He, Ne, and Ar) in a diverse suite of lunar mare basalts and soils, providing new insights about volatiles indigenous to the lunar interior, volatiles produced <i>in situ</i> at the lunar surface, and volatiles delivered to and implanted into the lunar surface. Simultaneous static-mode mass spectrometric measurements of these key volatiles, extracted from the same aliquot of sample by high-resolution stepped combustion, enable a more detailed identification of the different volatile components present by comparing their varying release patterns across a range of temperature steps. Taken in context with other studies of different volatile elements, this new data contributes towards a greater understanding of the Earth-Moon system, with additional implications for future <i>in situ</i> resource utilisation at the lunar surface. <br></br><br></br> With an average δ¹⁵N value of +0.93 ± 9.39 ‰, the indigenous N component measured in mare basalts is most compatible with a CO carbonaceous chondrite source for nitrogen in the lunar interior, although some caveats exist. Variations in abundance and isotopic composition of indigenous nitrogen imply a heterogeneous lunar mantle. Assuming up to ~50 % loss of solar wind ³⁶Ar from lunar soils, nitrogen trapped in soils can be reconciled with up to 87 % being contributed from a non-solar source with an isotopic composition of between +87 ‰ and +160 ‰. <br></br><br></br> Noble gases in soils are dominated by solar wind components, with only minor amounts of cosmogenic neon being released at the highest temperature steps. In mare basalts, noble gases are a mixture of trapped, radiogenic, and cosmogenic components (from which cosmogenic production rates can be calculated and exposure ages for previously undated samples suggested

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

The Open University

Year dc:date.issued

2016

Author dc:creator

• Mortimer, James Ian

Language dc:language

en