MSL - SAM and CHEMIN, Discussion of the science/results from these instruments Options

[Gerald]

According to the PDS, SAM has performed an "Atmospheric methane enrichment" experiment, level 2 reduced data here.
CH4 seems to have been identified by the TLS, file sm25206f0684rdr2__amet_tls_abundnc_1.csv:

"MOLECULE","VOLUME MIXING RATIO","ERROR"
"CO2 vmr",,
"H2O vmr",,
"CH4 vmr",0.90,0.16

I didn't find out absolute abundance, and can't assess, whether the methane is of Martian origin.
Hope, we'll learn more on the Monday telecon.

[serpens]

While the SAM PDS results show Methane as 0.9 under a Volume Mixing Ratio heading, I suspect that the measurement is in fact parts per billion, assuming that they conducted enrichment studies for the Tunable Laser Spectrometer.

[Gerald]

Not quite sure, whether the enrichment factor in this spyr_tls documentation is applicable to the amet_tls run, too, but it appears plausible:

The enrichment script was fully tested in the SAM test bed at GSFC to produce an enrichment factor of about 22. Provided data has this division already made to reflect the original Mars methane abundance with its correspondingly lower uncertainty.

The 0.90, with 1-sigma error 0.16, most likely referes to the volume ratio. The ratios for one analysis should sum up to 1.0, in theory.

As an example, sm25195f0637rdr2__adir_qms_atmcomp_1.csv (in this PDS subdirectory) reads

"SPECIES","VOLUME MIXING RATIO","UNCERTAINTY"
"CO2 region 1",0.959,0.018
"40_Ar region 1",0.02,0.0002
"N_2 region 1",0.019,0.0005
"O_2 region 1",1.70E-03,2.00E-04
"CO region 1",6.20E-04,1.00E-04
"CO2 region 2",0.96,0.02
"40_Ar region 2",0.019,0.0002
"N_2 region 2",0.019,0.0006
"O_2 region 2",1.60E-03,2.00E-04
"CO region 2",4.00E-04,1.00E-04

Region 1 sums up to about 1.0, region 2 to exactly 1.0.

[Don1]

I'm fairly sure that the methane number is some kind of error. The mixing ratio reported is far too high for it to be real. Due to a construction defect, SAM brought a sample of Florida atmosphere with it to Mars, and that had methane in it.

If they ever do detect methane, I would expect a quick press conference.

[Don1]

The team just announced at the AGU that they did see a brief burst of methane at a concentration of 7 parts per billion (ppb). They think that the source is local to Gale Crater. There wasn't enough methane to measure the isotope ratio of C12/C13, which might provide clues to the source.

They are also reporting a detection of organics in the rocks at Cumberland, which was drilled a few years back in Yellowknife Bay. They speculate that the organics are associated with concretions in the rock. They do not detect high levels of organics in the recent drill sample at Confidence Hills, or at Rocknest or John Klein. They didn't discuss Windjana.

Press release here

[Don1]

Here are some miscellaneous notes about inorganic SAM results.


Hydrogen isotopes and water: From deuterium measurements it looks like Mars had 2-3 times as much water when Lake Gale was around, maybe enough to cover the planet to a depth of 100-150m. Deuterium measurements show that Mars had lost much of it's initial water before Lake Gale was active.

Confidence Hills: Grotzinger mentioned sulfates. Sulfuric acid forms sulfate salts, and it is oxidizing, which might explain the presence of hematite. This will make the current location less suitable for organics than Yellowknife Bay. Volcanoes emit sulfur dioxide, so Confidence Hills may record a more volcanic Mars.

Chlorine isotopes: Values in Gale Crater are lighter than Martian meteorites and there is a difference between Windjana and Yellowknife Bay. That is weird. Isotope separations are difficult, and only a few processes produce them.

Curiosity still has a leftover sample of Cumberland material in the lab, according to one of Emily's tweets.

SAM detected reduced carbon in the Rocknest dust. This could mean something like charcoal or graphite.

Mars magmas were apparently enriched in chlorine, and would have supplied hydrochloric acid to the atmosphere. It is worth noting that there is a very rich chemistry of organic molecules which contain chlorine.

[jmknapp]

Going by the sols identified in the paper, marked on the attached map are the sites where the increased methane was observed (7.19 +/- 2.06 ppb).



EDIT: I see they provided such a map in the supplementary materials, figure 10.

Quoting from the paper:

The persistence of the high-methane values over 60 sols and their sudden drop 47 sols later is not consistent with a well-mixed event, but rather with a local production or venting that, once terminated, disperses quickly... The marginally higher daytime values suggested in sols 306 and 526 indicate a source to the rover's north, because prevailing daytime winds would advect toward the rover location... While we cannot rule out possible clathrate release or surface adsorption into the regolith with subsequent release, both these mechanisms do not support the local, short timescale variation we observe.

[marsophile]

The methane press release refers to measurements made in late 2013 and early 2014. The PDS entry discussed earlier here reported on a methane enrichment experiment performed in July 2014. Also the value reported there does not seem to match the figures in the press release. Not sure what to make of that. I guess if it is PPB, it is consistent with the other measurements.

[jmknapp]

The recent paper in Science discusses the enrichment runs including Sol 684 back in July. The enrichment runs allowed them to pin down the background methane concentration to a much tighter tolerance: 0.89 +/- 1.96 ppb for the "direct-ingest" runs vs. 0.69 +/- 0.25 ppb for the enrichment runs (95% confidence) .

It's interesting that they describe the TLS as having some methane contamination ("Florida air") in the foreoptics chamber, meaning the laser beam has to pass through 9cm of methane at tens of ppm levels before entering the main Herriott cell where it bounces many times between mirrors for a much greater path length (16.8 meters). So all the datasets show a methane signal and to get the level in the Martian air they must subtract the empty cell reading from the full cell reading. The raw empty cell readings show a much greater concentration of methane than the difference.

[Gerald]

Table 1 in the appendix of the paper (free access via here) contains a line

684 Jul 9th 2014 158.8 Night/4.5/2.7 0.90 ± 0.16 0.90 ± 0.32

This could correspond to the PDS entry. (I'm not yet quite sure.) In this case Serpens' suspicion (above) would have been correct.

[serpens]

While correlation does not necessarily mean causation (and vice versa) the lack of correlation to key variables such as temperature, water vapour/oxygen abundance and terrain removes any easy paths to explaining the transient and low level methane readings. Transient is a bit of a rubbery description as we have no way of telling just how long each incident lasted. I can well understand why they put a lot of effort from a lot of highly qualified people into analysing these readings before releasing the findings.

[Mercure]

...And the news has hit mainstream media ("methane burps"): http://www.independent.co.uk/news/science/...rs-9929510.html

[wildespace]

Speaking of the media, Yahoo and Space.com somehow latched on the discovery of water at Cumberland:
http://news.yahoo.com/curiosity-rover-dril...-122321635.html
http://www.space.com/28030-mars-water-curiosity-rover.html

Please refresh my memory - hasn't this been anounced a while ago, and isn't exacly news? It was water locked in minerals, such as clays, right?

So unless I'm mistaken, the only real news is those spikes in levels of methane.

[James Sorenson]

So unless I'm mistaken, the only real news is those spikes in levels of methane.

The organics discovery is new as well. Just a heads up, the Discovery Channel is airing a documentary tomorrow at 10pm EST called "Red Planet Rover" featuring the new findings.

https://www.youtube.com/watch?v=TOhBDy4e_ec

[serpens]

Not really new as they noted detection of di-chloropropane and chlorobenzene back in 2013 but whether Martian or contaminants from earth was open. I guess they are thinking chlorinated alkanes in the drill sample? Given that there was sometime between Phoenix's confirmation of perchlorates and mission launch I wonder if they investigated means of removing these oxidants in the first instance.