[X] My Assistant

[dudley]

It's been reported today that a release of methane on Mars, three times larger than ever detected before, was discovered on Wednesday. On Friday the Curiosity rover had its plans altered, in order to concentrate on this phenomenon, it's said. Preliminary results of this investigation are expected on Monday. Further information is available in the article, linked below:

Link

[nprev]

Hmm. On that note, I've heard very little about SAM's ability to detect perchlorates and peroxides. I assume that they are far too volatile to be inferred from GCMS data?

[JRehling]

That's a good point, but also, GCMS only provides the mass of a molecule and that becomes ambiguous for large molecular weights (and sometimes, for smaller ones like CO vs N2). Not only do different substances have the same MW, but different isotopes of one substance will have results ±1, ±2 (etc) of the mode.

Perchlorate molecules would have a molecular weight of about 100-200, and then you're left to interpret what compound produced a result of, say, 138.

[mcaplinger]

GCMS only provides the mass of a molecule and that becomes ambiguous for large molecular weights...

Mass spectrometry has that limitation, but AFAIK gas chromatography doesn't. And SAM has many wet-chemistry and evolved-gas modes for perchlorates as well.

See, for example, "Evidence for perchlorates and the origin of chlorinated hydrocarbons detected by SAM at the Rocknest aeolian deposit in Gale Crater"
https://agupubs.onlinelibrary.wiley.com/doi...1002/jgre.20144