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MSL - SAM and CHEMIN, Discussion of the science/results from these instruments
serpens
post Jun 11 2018, 03:44 AM
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QUOTE (Dalhousie @ Jun 10 2018, 11:02 PM) *
After this length of time and the many purgings I'd be sceptical of this assertion. The efforts to write off evidence of Mars methane by some seem to become ever more desperate attempts of straw clutching.

The fore-optics chamber is not purged. Small concentrations of methane have been measured in the Martian atmosphere and since that atmosphere is itself what we would classify on Earth as an industrial level vacuum the actual amount of methane is minute - but it is there. The seasonal variation in ppb must also take account of the cyclical variation in atmospheric pressure as CO2 transfers between summer/winter poles and this in itself means that the source of the methane spikes is not necessarily local. The real question is what causes the atypical spikes and at present no-one really knows. But I have seen no attempts to write off evidence of methane.
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Dalhousie
post Jun 11 2018, 04:36 AM
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QUOTE (serpens @ Jun 11 2018, 04:44 AM) *
The fore-optics chamber is not purged. Small concentrations of methane have been measured in the Martian atmosphere and since that atmosphere is itself what we would classify on Earth as an industrial level vacuum the actual amount of methane is minute - but it is there. The seasonal variation in ppb must also take account of the cyclical variation in atmospheric pressure as CO2 transfers between summer/winter poles and this in itself means that the source of the methane spikes is not necessarily local. The real question is what causes the atypical spikes and at present no-one really knows. But I have seen no attempts to write off evidence of methane.



Kevin Zahnle has been an outspoken critic of methane on Mars on several occasions.
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marsophile
post Jun 11 2018, 05:34 AM
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Methane signals due to contamination, if present, should show a gradually diminishing trend over time.

What are the prospects for Curiosity obtaining isotopic signatures of methane detections given enough time? Perhaps Florida air might have a unique and recognizable signature that could be distinguished even with rough measurements.
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serpens
post Jun 11 2018, 08:51 AM
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Not really an outspoken critic surely. Kevin Zahnle agreed that the methane signature exists. He simply suggested that the spike could have come from the rover. At the time in particular that had to be a consideration.
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MrNatural
post Jun 11 2018, 12:45 PM
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Could the methane be off-gasing from plastics on MSL? Or breakdown products of plastics exposed to UV and temperature swings?
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mcaplinger
post Jun 11 2018, 03:11 PM
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QUOTE (MrNatural @ Jun 11 2018, 04:45 AM) *
Could the methane be off-gasing from plastics on MSL? Or breakdown products of plastics exposed to UV and temperature swings?

Read the paper, it's online. http://science.sciencemag.org/content/360/6393/1093.full

QUOTE
We argue against the possibility that the rover itself is a source of methane because we cannot identify any source large enough to produce even an instantaneous cloud of ~7 ppbv methane in a 10-m-diameter sphere around the rover...



--------------------
Disclaimer: This post is based on public information only. Any opinions are my own.
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Dalhousie
post Jun 12 2018, 12:37 AM
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QUOTE (serpens @ Jun 11 2018, 08:51 AM) *
Not really an outspoken critic surely. Kevin Zahnle agreed that the methane signature exists. He simply suggested that the spike could have come from the rover. At the time in particular that had to be a consideration.


Ge has reacted negatively to every major methane report since 2004. So he has got previous....
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