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View Full Version : Methane in Martian atmosphere may not be an indication of life



starcanuck64
2013-May-29, 10:09 PM
http://www.mpg.de/5825479/mars_methane_life


Without an expedition to Mars and with nothing more than a meteorite to help them, researchers at the Max Planck Institute for Chemistry in Mainz and the universities in Utrecht and Edinburgh have now found a major source. “Methane is produced from innumerable, small micro-meteorites and interplanetary dust particles that land on the Martian surface from space,” explains Frank Keppler, lead author of the study now published in the research journal Nature. “The energy is provided by the extremely intense ultraviolet radiation,” adds the atmospheric chemist.


Together with colleagues from Great Britain and the Netherlands, the researchers from Mainz irradiated samples of the Murchison meteorite with ultraviolet light. “The meteorite contains several percent carbon and has a similar chemical composition to most of the meteoritic matter that lands on Mars,” says the cosmochemist Ulrich Ott. The 4.6 billion-year-old meteorite fell to Earth in 1969 in the Australian town of Murchison. The researchers selected conditions identical to those on Mars for the UV irradiation, which caused considerable quantities of methane to escape from the meteorite almost immediately. Their conclusion: carbonaceous compounds in the meteoritic matter are decomposed by the high-energy UV radiation, and methane molecules are formed in the process.

iquestor
2013-May-29, 11:29 PM
wow. great article, and great research; although I was hoping it was a clear indication of microbes. :(

TooMany
2013-May-29, 11:33 PM
It's certainly a possible alternative explanation. I'm not sure any scientists have claimed that the detection of methane is direct evidence of life on Mars.

That meteorite is a carbonaceous chondrite. About 5% of meteorites fall into this category. They contain organic compounds and water in addition to silicates, oxides and sulfides.

I wonder what the fate of methane is in the Martian atmosphere. Can it perhaps get converted to CO and water by interaction with CO2 and sunlight? Perhaps the perchlorates on the surface are a sink?

Selfsim
2013-May-30, 12:30 AM
Several comments:

0) the research was announced is prior to Curiosity/MLS/SAM analyses.

i) The Murchison meteorite is a very rare find as far as terrestrial meteorites are concerned because it contains a high amount of complex organic compounds. As these researchers were out to test their hypothesis of whether methane could be produced, presumably, they selected specifically, the Murchison meteorite, in order to make sure the base compounds were already present.

Did their research take into account the relative rarity of Murchison type meteorites, especially in making the assumption that sufficient of these meteorites actually fall on Mars in the first place, (to generate the methane)?

ii) If Murchison type meteorites are common on Mars, (and evenly distributed to the point they can generate the methane), why hasn't the correspondingly significant quantities been detected by Viking or Curiosity? (This might be a 'wait-and-see' and a function of the almost insignificant testing done so far on Mars, admittedly ..)

iii)
“Methane is produced from innumerable, small micro-meteorites and interplanetary dust particles that land on the Martian surface from space,” explains Frank Keppler, lead author of the study now published in the research journal Nature.I find this statement to be very poorly worded, and is too easily taken out of the context of the paradigm of the hypothesis being pursued in the lab.

iv)
“The meteorite contains several percent carbon and has a similar chemical composition to most of the meteoritic matter that lands on Mars,” says the cosmochemist Ulrich Ott.This statement also appears unsupported by direct evidence from Mars. (It was thus prematurely released .. why?).

v)
Their conclusion: carbonaceous compounds in the meteoritic matter are decomposed by the high-energy UV radiation, and methane molecules are formed in the processWhat they appear to have actually shown in the lab, is that:
"carbonaceous compounds in the meteoritic matter of the Murchison meteorite, are decomposed by the high-energy UV radiation, and methane molecules are formed in the process."

Overall, its just another hypothesis, which has some empirical lab test results and very specific, speculative assumptions behind it.

IMO, I'd be waiting for (a lot more) test results from Curiosity's SAM TLS, GCMS and QMS before making such bold statements. It seems the primary motivation (from the article) for making such statements, might be in response to the overly unjustified public expectation, that the methane on Mars is caused by biology, (as indicated by the comments made by the article's author).

(Its a pity that the SAM equipment seems to be influenced by contaminants at present …)

starcanuck64
2013-May-30, 08:16 PM
Even if there is some production of methane from the bombardment of material from carbonaceous meteorites on the planet surface the study does leave room for a biological origin for a portion also.


The results obtained by Frank Keppler’s team should bring “down to earth” all those who firmly believe in the biological origin of the methane. The researchers cannot fully exclude the hypothesis of Martian microbes, however, because, although the process found here is inevitable, it is quite possible that further processes contribute to methane production. The researchers hope that Curiosity, the Mars Rover that NASA expects to land on our neighbouring planet at the beginning of August, will provide more details on the formation of methane, and maybe even final clarification as to whether there is life on Mars.

And as Selfsim states there may be limitations to how applicable this is to Mars.

ASTRO BOY
2013-Jun-08, 09:28 PM
Several comments:

[/I]Overall, its just another hypothesis, which has some empirical lab test results and very specific, speculative assumptions behind it.






And of course there is nothing wrong with that.....It's all part of the scientific process.....we observe, speculate and assume, sometimes it turns out to be validated, other times it is invalidated.
In my opinion, until we are able to have a more hands on approach to Mars, it has not yet conclusively ruled out the existence of some form of life.......still....although the odds are lengthening.

Spacedude
2013-Jun-11, 02:37 PM
Perhaps my understanding of this is incorrect but I had thought that the methane detected on Mars was both seasonal and localized. If it is more uniform around the surface of Mars then the study above may have merit.

Colin Robinson
2013-Jun-11, 06:26 PM
Perhaps my understanding of this is incorrect but I had thought that the methane detected on Mars was both seasonal and localized. If it is more uniform around the surface of Mars then the study above may have merit.

If you read right thru the article linked to by the opening post of this thread, it mentions that production of methane from meteorite fragments in Martian conditions would vary with temperature. So arguably consistent with different concentrations in different seasons and regions.

starcanuck64
2013-Jun-11, 06:47 PM
Perhaps my understanding of this is incorrect but I had thought that the methane detected on Mars was both seasonal and localized. If it is more uniform around the surface of Mars then the study above may have merit.

This is the section from the article that involves why the methane concentration may be seasonal and localized.


Since the temperature on the red planet varies from minus 143 degrees Celsius at the poles to plus 17 degrees Celsius at Mars’ equator, the scientists also investigated the meteoritic samples at appropriate temperatures. The warmer it became, the more methane was released by the meteoritic fragments. This temperature dependence also agrees with the different methane concentrations at different locations in the Martian atmosphere. In infrared spectra, the largest concentration of methane was found in the equatorial region, the warmest place on Mars, relatively speaking.

Spacedude
2013-Jun-11, 11:25 PM
Thanks for pointing that out, got it now. I'm probably a bit biased on the side of underground oasis type environments with microbial activity.

Don J
2013-Jun-12, 05:01 AM
Perhaps my understanding of this is incorrect but I had thought that the methane detected on Mars was both seasonal and localized. If it is more uniform around the surface of Mars then the study above may have merit.
Your understanding of this is correct.
Here the European Space Agency report -New in-depth analysis made by the Planetary Fourier Spectrometer (PFS) data also confirms that methane is not uniform in the atmosphere, but concentrated in some areas.-
http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Water_and_methane_maps_overlap_on_Mars_a_new_clue2


ESA PR 51-2004. Recent analyses of ESA’s Mars Express data reveal that concentrations of water vapour and methane in the atmosphere of Mars significantly overlap.

This result, from data obtained by the Planetary Fourier Spectrometer (PFS), gives a boost to understanding of geological and atmospheric processes on Mars, and provides important new hints to evaluate the hypothesis of present life on the Red Planet.
PFS observed that, at 10-15 kilometres above the surface, water vapour is well mixed and uniform in the atmosphere. However, it found that, close to the surface, water vapour is more concentrated in three broad equatorial regions: Arabia Terra, Elysium Planum and Arcadia-Memnonia.

Here, the concentration is two to three times higher than in other regions observed. These areas of water vapour concentration also correspond to the areas where NASA’s Odyssey spacecraft has observed a water ice layer a few tens of centimetres below the surface, as Dr Vittorio Formisano, PFS principal investigator, reports.

New in-depth analysis of PFS data also confirms that methane is not uniform in the atmosphere, but concentrated in some areas. The PFS team observed that the areas of highest concentration of methane overlap with the areas where water vapour and underground water ice are also concentrated. This spatial correlation between water vapour and methane seems to point to a common underground source.

Spacedude
2013-Jun-12, 01:28 PM
Thanks DonJ for reinforcing my bias :). The answer to the methane source can be more than just one source, so it's still up in the (Martian) air, what little there is of it.

iquestor
2013-Jun-13, 01:31 PM
Has MSL recorded any yet? I know initial readings were negative.

Don J
2013-Jun-13, 07:52 PM
Has MSL recorded any yet? I know initial readings were negative.
Here a report from April 10, 2013
http://www.spaceflight101.com/msl-sam-science-reports.html


The SAM team also continued to analyze previous data that focused on the search for Methane. So far, the SAM data suggests a Methane abundance of 0.4 +/-1.1ppbv with an upper limit of 2.7ppbv at a 95% certainty level. A definitive Methane measurement has yet to be made and for that, SAM will be performing Methane Enrichment Experiments in the future to increase its sensitivity in order to detect Methane and possibly its isotopes.