I just glanced into it. Methane was detected - in very minute amounts, like all other components of the lunar "atmosphere" - and in this paper (warning! 8MB PDF) it is speculated that it is formed from surface reactions of carbon and hydrogen from the solar wind.

And, yes, HST can image the Moon. But no telescope operational or planned can resolve Apollo landing artifacts from Earth or Earth orbit. (Yes, I know the Moon is in Earth orbit. You know what I mean.)

ETA: ToSeeked by 69₁₀. Also, I'm pretty sure, as already indicated by others, the tenuous lunar atmosphere can't be detected by HST spectrometry. It took sensitive in situ measurements by the ALSEP devices to do a census of the Moon's gases.

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