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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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marsophile
post Jan 2 2019, 01:02 AM
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https://www.digitaltrends.com/cool-tech/mars-methane-tgo/

Does anyone who attended the referenced AGU session (https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/350159) know anything about this? The linked abstract does not mention it. Although perhaps not inconsistent, it seems to contrast sharply with the Curiosity findings.

[EDIT 01/5/19: A more detailed report here:
https://earthsky.org/space/esa-exomars-trac...missing-methane
which includes a link to a Science news item:
https://www.sciencemag.org/news/2018/12/mar...iously-vanished
]
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marsophile
post Apr 5 2019, 07:28 PM
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http://spaceref.com/mars/mysterious-martia...-confirmed.html

This answers some questions. The methane spike detected by MSL seems to have been confirmed, and its source determined to be east of Gale Crater.
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marsophile
post Jun 22 2019, 09:05 PM
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https://www.engadget.com/2019/06/22/curiosi...ts-methane-gas/

Another methane spike, said to be 3 times larger than the previous largest.

First reported in the New York Times (limited access).
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Explorer1
post Jun 22 2019, 09:50 PM
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Combined with the negative TGO results, definitely a complex picture emerging. Will there be a press release soon?
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marsophile
post Jun 24 2019, 12:08 AM
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It was reported that some additional tests would be done over the weekend, and some results might be received tomorrow. There is this at nasa.gov:

https://www.nasa.gov/feature/jpl/curiosity-...-methane-levels

Maybe the quantity of methane involved is enough to do carbon isotope analysis? That might help to discriminate between possible sources.

If this is confirmed by other assets, but not by TGO, I will start to wonder if the TGO methane detector is non-functional. The simplest explanation for a complete non-detection might be a broken detector.
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Gerald
post Jun 24 2019, 01:22 AM
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The TGO instruments, NOMAD and ACS, are spectrometers, and shouldn't be specific to some given trace gas. They detected other species very accurately.

The methane release detected by MSL might be very local.
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serpens
post Jun 24 2019, 02:43 AM
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Using solar occultation which I believe covers sampling for trace gases including CH4 in a vertical atmospheric column, the sampling rate is around a kilometre per second from the surface up to 200 km altitude. So the fotprint of TGO is limited and TGO's orbit may or may not pass over the area of the methane pulse before it dissipates.

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Explorer1
post Jun 24 2019, 03:26 AM
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Press release is out; not much more details for now: https://www.jpl.nasa.gov/news/news.php?feature=7433

QUOTE
The SAM team organized a different experiment for this weekend to gather more information on what might be a transient plume. Whatever they find - even if it's an absence of methane - will add context to the recent measurement.

Curiosity's scientists need time to analyze these clues and conduct many more methane observations. They also need time to collaborate with other science teams, including those with the European Space Agency's Trace Gas Orbiter, which has been in its science orbit for a little over a year without detecting any methane. Combining observations from the surface and from orbit could help scientists locate sources of the gas on the planet and understand how long it lasts in the Martian atmosphere. That might explain why the Trace Gas Orbiter's and Curiosity's methane observations have been so different.
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