Possibility of the Presence of S, SO2, and CO2 at the Poles of the Moon

摘要

Thepresenceofvolatilesnearthelunarpolesisconsidered.Thechemicalcompositionofalunaratmospheretemporarilyproducedbycometimpactisanalyzedduringthedayandnight.C-richandlong-periodcometsareinsufficientsourcesofwatericeontheMoon.O-richshort-periodcometsdeliversignificantamountsof$$mathrm{H}_{2}mathrm{O}$$,$$mathrm{CO}_{2}$$,$$mathrm{SO}_{2}$$,andStotheMoon.AnobservableamountofpolarhydrogencanbedeliveredtotheMoonbyasingleimpactofanO-richshort-periodcometwithdiameterof5a€‰kmintheformofwaterice.Theareaswhere$$mathrm{CO}_{2}$$and$$mathrm{SO}_{2}$$icesarestableagainstathermalsublimationareestimatedtobe300and$$1500,mathrm{km}^{2}$$,respectively.Ifwatericeexistsinthe2a€‰cmtopregolithlayer,$$mathrm{CO}_{2}$$and$$mathrm{SO}_{2}$$icescanbestableinthecoldestpartsofpermanentlyshadedcraters.Thedeliveryrateofelementalsulfurnearthepolesisestimatedtobe$$10^{6},mathrm{g},mathrm{yr}^{-1}$$.Thesulfurcontentisestimatedtobeashighas1a€‰wt%inthepolarregions.TheSELENEgamma-rayspectrometercandetectsulfurpolarcapsontheMoonifthesulfurcontentishigherthan1a€‰wt%.Thisinstrumentcancheckthepresenceofhydrogenandmineralswiththeunusualchemicalcompositionatthelunarpoles.