Identification of surface hydrogen enhancements within the Moon’s Shackleton crater

Abstract

Bulk surface hydrogen enhancements have been identified within the Moon’s Shackleton crater. Using an analysis of fast and epithermal neutron data from the Lunar Prospector mission, the permanently shadowed region (PSR) within this crater has a surface concentration of 0.72±0.13wt.% water equivalent hydrogen (WEH). In contrast, hydrogen enhancements within other polar PSRs such as Cabeus are likely buried under more than 10cm of hydrogen-poor regolith. Subsurface hydrogen absent a surficial counterpart implies an episodic delivery mechanism. The burial depth suggests the epoch of hydrogen deposition was at least 100myr ago if impact gardening is the dominant mechanism for volatile transport to depth. Shackleton crater’s surface enhancement may be related to its thermal environment, ∼30K warmer than other south pole PSRs, in which thermal processes control the vertical migration of hydrogen within Shackleton but inhibit migration in colder regions. One sentence summaryEnhanced bulk surface hydrogen concentrations have been identified within Shackleton crater, giving insights into volatile delivery and transport processes within permanently shadowed regions at the Moon’s poles.