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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
Julius
What about trace gas orbiter? Insight should also detect tectonic activity if the methane has a geological source. In the absence of any activity, it may be interpreted as boosting the idea of methane arising from a biological source.
JRehling
Nice thought, Julius, but I'd say "could" rather than "should." Gas release could be arbitrarily gentle. We're talking about an unknown phenomenon so it's impossible to nail down the details. This could even be a chemical release from a source with a geological origin. But, yes, certainly some kinds of gas release would have a seismic parallel, and having the ability to check that is a wonderful capability.
HSchirmer
QUOTE (JRehling @ Jun 22 2019, 07:40 PM) *
Gas release could be arbitrarily gentle.
(snip)
This could even be a chemical release from a source with a geological origin.


Thinking along similar lines, estimates suggest the Gale crater could have punched as deep as 17kM deep, compared to ~11kM for the Marianas Trench.

On Earth, that is easily deep enough for some really unusual physical chemistry, e.g. methane clathrates and subsurface pools of liquid CO2



So, there's a fair chance that this could be related to the breakdown of methane clathrates, aka "Burning Ice", which then collect and follow the many deep fractures likely created by the Gale impact.
Gerald
Regarding the brainstorming about the origin of the CH4, I've two almost entirely different lines of thoughts or questions:
1. Have exogenic causes been ruled out? I'm thinking of CH4 bearing cometary remnants. Impacts would be seasonal, when Mars would cross the orbit of the debris. They may cause local peaks of trapped gasses.
and 2. May the local clay be able to trap CH4 of an ancient CH4 atmosphere, and release traces of it during summer? Methane is a well-known strong greenhouse gas, and assuming an ancient CH4 atmosphere reminiscent of Titan may help to resolve the faint young Sun paradox for Mars.
Explorer1
If it was a regular meteor shower the orbiters would have noticed an increase in dust impacts, wouldn't they? There also doesn't seem to be a regular pattern of when the spikes occurred during the Martian year, and Curiosity has been watching for several of them so far.
Gerald
Similar attempts to correlate presumed methan spikes with meteor showers have been attempted or suggested before, see for instance the two articles
- A cometary origin for martianatmospheric methane:
QUOTE
The areal extent of meteor showers is in agreement with the areal extent
observed for martian methane plumes. Meteor showers typically peak over a
course of hours, depositing material onto an area that can be sub-hemispherical
in extent (Jenniskens, 1995), which is in agreement with the size of the Mumma
et al. (2009) plume.

- TESTING THE MARTIAN METHANE FROM COMETARY DEBRIS HYPOTHESIS: THE UNUSUALLYCLOSE 24 JAN 2018 INTERACTION BETWEEN COMET C/2007 H2 (SKIFF) AND MARS.

And there is a long list of candidate small bodies.

So, I was wondering, why this approach doesn't appear to be mentioned in the article linked to in post #1 of this thread. A possible reason would be an analysis that escaped my notice.
dudley
QUOTE (Julius @ Jun 22 2019, 09:26 AM) *
What about trace gas orbiter? Insight should also detect tectonic activity if the methane has a geological source. In the absence of any activity, it may be interpreted as boosting the idea of methane arising from a biological source.

This linked article from Nature explains that the Trace Gas Orbiter has not detected methane anywhere on Mars, so far, but is now directing its gaze at the site of the latest spike, in Gale crater. ESA's Mars Express, the other orbiter capable of detecting methane, is also looking there, it's reported.
The article also quotes one of the scientists in charge of the methane-detecting instrument on Curiosity, as calling the methane spike 'excitingly huge'. No word, yet from NASA, about the results of this weekend's investigations.

link
nprev
It would be interesting to know if SEIS on InSight captured any possible tremors shortly before this event, but it's possible that the recent mole recovery efforts may have introduced too much noise to make detection of such a signal unambiguous.
djellison
...and it's gone.

https://twitter.com/Shamrocketeer/status/1143312546717261824

.
QUOTE
@MarsCuriosity SAM instrument PI Paul Mahaffy confirms to #AbSciCon2019 that a ‘plume’ of methane at 21 ppb was seen last week, disappeared over the weekend.
dudley
There's an outside chance that the Mars Express Orbiter caught the methane spike, too. It will apparently be some time before it downloads its data to Earth.

It's reported that the Trace Gas Orbiter could use a methane spike of this concentration (~20 ppbv) to distinguish between carbon 12 and carbon 13. An unexpected excess of the lighter isotope could argue against geological and astrophysical explanations.
Steve5304
Wild speculation:

Could it be stowaway crap from earth that got lucky? Bacteria evolve really quick.
marsbug
Life, as they say, finds a way.... but IMHO it's not likely on the Martian surface thanks to the sterilising action of the UV content of the Martian sunlight. And you'd need water to be present on or near the rover: It's not totally impossible across the whole range of Martian conditions for small amounts of liquid h2o to exist, but unlikely. Unless anyone can think of a way in which the presence of the rover might generate more favourable conditions for the formation of small amounts of liquid water, or act as such a favourable environment itself, I would comfortably dismiss the idea on those grounds alone, cool though it would be to colonisation fans.
nprev
And a reminder to all to read & heed rule 1.3.
Steve5304
QUOTE (nprev @ Jul 19 2019, 09:45 PM) *
And a reminder to all to read & heed rule 1.3.



Was this in reference to my post? Its a perfectly rational argument. We could potentially contaminate mars. Well at least certain parts of the rover shielded from radiation

nprev
This was a general reminder to remember 1.3 given the nature of the topic.
serpens
The previous methane spike was detected by both Curiosity and Mars Express and appears to have originated in Aeolis Mensae, East of Gale. This area is a tectonic transition zone with probable buried ice. I believe the hypothesis is that occasional fracturing of the ice releases small amounts of methane that have accumulated in pockets beneath the ice. If there is liquid water deep down wouldn't ongoing serpentinization be a possibility?
jccwrt
A theme from the methane session at 9th Mars was that Curiosity measurements and TGO observations are possibly irreconcilable (supposing the Curiosity measurements are natural methane and not rover-generated). There were a couple of working hypotheses which might be working in tandem with one another to prevent TGO from seeing much methane.

First is that the planetary boundary layer collapses overnight, and within a well-protected crater it might only be several meters thick. If the methane is produced locally, it could build up to a relatively high concentration under a temperature inversion. Then once the sun rises the boundary layer rapidly expands and mixes out the gas. This would prevent TGO from seeing the methane at high levels because TGO takes its observations post-sunset, when the boundary layer is at its most mixed. The problem is that while this goes some way towards explaining the methane measurements it really only works under the presumption that there are only a few localized sources of methane, and that we got lucky and landed at one of those sources.

The other one is some mechanism of fast oxidation near the surface. These could be things like hydrogen peroxide (probably generated by electrostatic effects during dust storms) or some other nasty volatile adsorbed onto dust grains. Any methane released into the atmosphere would quickly interact with these adsorbed oxidants and be destroyed. This mechanism could do the trick, but it's not particularly well-constrained. Short of directly measuring how methane reacts with dust particles (which I don't even know how to go about doing with the current equipment on Mars) I'm not sure how well this works in practice.

At any rate, TGO can only see down to about 5 km above the surface, so if there's some mechanism destroying methane near the surface TGO is never going to see it.
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
QUOTE (JRehling @ Jul 28 2019, 03:43 PM) *
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
marsbug
Ahem. If I might pedant.... many moons ago I used to build GCMS. So, for the uninitiated (feel free to skip this first paragraph if you already know how GCMS work): The Gas Chromatograph stage works by flash heating the sample and seeing how long the components of the vapour take to travel down a long, thin, column (more like a rolled capillary tube, usually) with one of a range of coatings on it's inner surface that slow the different vapour components down by differing amounts. The GC gives you a rough idea of what is in the sample based on how long different pulses of vapour components take to hit the detector at the end of the column. In the GCMS the Mass Spectrometer is the detector. This takes the material in the pulses exiting the GC stage, ionises it (aiming to average 1 charge per molecule), and separates the molecules in it according to their charge to mass ratio. So, crudely speaking, you get a rough idea from the GC, then a more detailed analysis from the MS.

OK, here's why I'm pedanting at you all: The important point for large molecules is that when you ionise them they almost always break apart - and for a given type of ionisation method most large molecules break apart in a predictable, repeatable, fashion. So you don't get a big signal at the charge to mass ratio for the parent molecule, you get a 'fingerprint' of smaller peaks that is unique to a given high mass molecule. For example, even something fairly light weight like the amino acid glycine (mass 75 AMU) yields a fingerprint like the one I've attached when ionised by electron bombardment (see attached file). Notice that the biggest peak isn't at 75 AMU, but at 30.

So the MS isn't simply analysing heavy molecules by their charge / mass ratio - in fact that almost certainly wouldn't work. It's using these heavy molecule specific fingerprints. It can be very, very, specific as long as the molecule is known or modelled in how it breaks down under ionisation. When combined with the GC stage, and a database of known GC and MS 'fingerprints' this can be a very precise process for identifying heavy molecules.

It can go wrong : Getting the right rate of GC heating, GC column type, ionisation process and mass to charge ratio analyser stage all needs some idea to start with of what type of thing you'll be analyzing. But in this case the team behind the GCMS on the rover will have had that from previous missions.

Now, that's probably clear as mud. And, if my old boss is here he will probably now tear me apart for that explanation anyway... go ahead Vic, I'm sure I deserve it.
serpens
Thanks for the explanation Marsbug. The mud was extremely transparent. So in the event of anomalous breakdown fingerprints, provided that a duplicate GCMS design is held it should be possible to run samples against the same setting variables in a lab to ascertain the identity of a molecule?
marsbug
Exactly. Unless I'm very much mistaken there will be a carbon copy of the rover's GCMS sitting in a NASA lab here on Earth, and one of its duties will be exactly that. Replicating a new fingerprint(s) may be a bit of an art, but they will have a good idea of what kinds of materials they need to start with in the Martian environment.

As an aside: I am very interested to see how this system flies when we get to environments with lots of very complex unknown organics, formed under hard to replicate conditions, such as Titan! I suspect they will already be building a database using reactions that can take place at cryogenic temperatures but that, as they say, is a different story.
marsbug
I just found this breakdown of the SAM lab, and including the GCMS. Good lord, she's a monster - six columns on the GC. I hated swapping columns on a single column system, this would drive me insane... Not that the columns can be changed on Mars, so I guess that makes sense since on Earth we could just swap the columns out to tackle different sample types. The article really hammers home that the GCMS is part of a battery of interconnected chemical analysis systems in SAM. I suspect that anything SAM as a whole truly cannot identify on its own will be real 'sit up and pay attention' stuff
JRehling
That's a superb explanation, marsbug! Thanks for elevating the discussion!
atomoid
more recent detail on the 'boundary layer collapse' mentioned earlier by jccwrt
https://www.sciencenews.org/article/overnig...methane-mystery
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