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Meet the Methanogens

Most Americans are emerging bleary-eyed from a tryptophan induced coma today and grudgingly marching back to work after a glorious extended weekend. In this twittering multimedia digital world many stories compete for a slot on our rested minds. The scary looming fiscal cliff and backroom dealings in DC that might fail to ease us down its gentle slope, the political back-and-forth back stabbing continues unabated as Republicans wrestle with ballot box defeat and Democrats continue to come out of the decades long reflexive crouch. It would be easy to miss what could turn out to be the most important story of the season. Right now its mere speculation over tantalizing hints, past and present, centered not on the third rock from the sun, but a more enigmatic planet, the fourth world out. NASA’s Mars Curiosity rover may have found something interesting in the arid frozen soil of the Red Planet. Right now the smart money is on a substance called methane.

Methane is CH4, it is a flammable gas, a viscous liquid, or a solid rock depending on temperature. It’s everywhere, a common compound in the universe and in our solar system. The tell-tale spectral signature of methane has been found in distant nebulae and on nearby moons and comets. Titan, the largest moon of Saturn, is swaddled in the stuff. Clouds of methane and related compounds are so thick on Titan that they concealed the surface from us until a plucky lander called Huygens finally floated through the thick atmosphere and landed in 2004. As expected Huygens revealed the frozen orange-yellow tableau characteristics of methane slush in large quantities shown right.

The methane floating through the cosmos in thin sheets and filaments, along with the lodes on large satellites and comets in our solar system, are firmly believed to be non biological in origin. But on earth it’s a different story entirely. Because our planet is so active and because methane is so reactive, it’s quickly broken down, often by various oxidation reactions into water and carbon dioxide. But it’s also quickly replaced, in large part by living organisms. Some microbes are so methane-centric* they’re collectively referred to as methanogens. They’re everywhere, in marshlands and deep under the sea, even in your gut! Some of these extant methanogens are not too different and are likely direct descendents of some of the very same little critters that lived and bred and died on earth for billions of years before we big metazoans arrived. Geochemical evidence suggests that methane gas may have once been so thick in our own primeval atmosphere that it painted our air and oceans with traces of pastal yellows and oranges.

We know now that billions of years ago Mars was warmer and way wetter than it is today. If methanogens arose on earth, there’s no physical reason why the same organisms couldn’t have thrived in ancient Martian ponds and lakes. But how wet and warm was Mars? How long did that youthful blush last? Did Martian life gain a brief foothold only to be cruelly snuffed out? Or, if so, did some hardy organisms survive the eons, perhaps below the surface where the last remnants of precious water remain? Those are some of the questions Curiosity was designed to answer.

The great drying: Mars as it may have appeared billions of years ago on the left and Mars as it appears today far right

We also know earth and Mars have been exchanging material for eons; a large object strikes one world, ejecta is blown miles into the air, in some cases dust or chunks of one planet is blown clear into interplanetary space where they might drift forever. But occasionally some of that same stuff gets near enough a large object like a planet to streak in like any other meteor. We’ve found pieces of the moon, Venus, and Mars here on earth. There’s no reason to think this is a one way phenomenon. Microbes ae hardy, a single particulate too small to see without a magnifying glass could host millions of them, and tiny grains of dust don’t burn in, they have so much surface area to volume that they never really heat up, they just settle into the atmosphere and gently fall to the surface. Microbes could easily hitch a ride, who’s to say where methanogens originally evolved? Our distant one-celled ancestors could have arisen first on Mars for all we know.

Today entire communities of extremophiles still thrive in terrestrial pockets of methane. Hot smokers and cold seeps supporting rich communities of invertebrates and fish, even specialized “meth worms” chewing through meth ice gracing the top of this post, are well documented examples of life’s tenacity and diversity. It’s also damn useful for us: methane is the primary alkane in natural gas, the same stuff that heats our homes and roasted millions of turkey’s last week. Plus, if you used any plastic on the Thanksgiving table, you probably depended on natural gas used in the production cycle as both energy and source material.

Methane is soluble in water, where there is liquid water astrobiologists speculate alien microbes might not be far away. So when minute traces of methane were detected in the wispy thin Martian atmosphere a few years ago, scientists were excited. When the rovers Spirit and Opportunity found signs of ancient flowing water on the surface and then Phoenix founds big blocks of ice just under the sand, the excitement built even more. The thing that really made hairs stand on end was the CH4 traces seemed correlated with Martian seasons, the gas appeared in summer. But since then confirming methane has been elusive. So it’s not surprising that some of the instruments aboard Curiosity are specially designed to sniff out and analyze any whiff of both methane and water. Which brings us to last week.

A flurry of excitement and speculation about something found by one of those instruments kicked off, sadly it was right before Thanksgiving, media and NASA heads were out, so it’s hard to say if the excitement conveyed by some researchers will be as exciting to the laypublic. To make matters worse NASA vaguely backpeddled and then clammed up completely. There is an announcement now scheduled for Dec 3.

The ginormous question is what have they found? The smart money is on methane because the instruments involved include devices calibrated for detecting it. If so, there is a good chance it’s a false positive — it wouldn’t be the first time and that explains NASA’s caution. There’s a chance it is methane but it could be completely non biogenic in nature. It could be something completely unrelated to methane, signs of recent liquid water for example … or it could be an utter PR failure and there could be nothing of significance at all.

Or we can dream it could be important enough that it will outlive all of today’s major headlines of fiscal cliffs and terrorist strikes, methane combined with signs of biological molecules for example, which would all but confirm recent micorbial life on Mars just under the surface, right where some courageous scientists have speculated it was all along. Make no mistake, a few molecules like that would be the beginning of an age of extraterrestrial discovery the likes of which will be taught to legions of children for hundreds of years to come. Something you will always remember, the early 21st century, the time when humans from the planet earth first learned we are not alone in the universe.

Bottom line, until NASA releases whatever findings they have we’ll just have to wait. But no matter what happens, then, to quote Clarke,I don’t think we’ll have to wait long.


  1. F says

    Methanogens produce methane, and like most critters, are not exactly happy in an environment rich in their own waste. Methanotrophs, on the other hand, are quite happy to chow on methane. Further, methylotrophy is not limited to methanotrophy, so more fun there. Also, a lot of the metabolism going on around seafloor vents involves hydrogen sulfide rather than methane.

    (F — I have edited that portion of the orignal post and placed a star for reference due to your comment, thanks — DS)

  2. Trebuchet says

    Since it doesn’t seem as if methane would be particularly stable on Mars, would the presence of methane indicate CURRENT biological processes? Or is methane more stable on Mars than on earth?

  3. says

    My money’s still on an announcement that Obama was part of a CIA mission where he was teleported to Mars.

    Either that, or the announcement that Nibiru is real after all, and will hit the Bahamas around Dec. 21. And will become visible in the sky on Dec. 4. Gives you a couple of weeks to say goodbye to your neighbors and all that.

    Oh yeah. Let’s stick with the crazy.

    Which reminds me: have to check with the YouTube conspiracy bunch. This ought to be quality entertainment.

  4. Trebuchet says

    I’ve actually been waiting for the conspiracy theory to show up that the announcement is just an Obama plot to take attention away from Benghazi. Passively waiting, that is, I’m not about to soil my computer by going out and looking for it!

  5. anubisprime says

    Trebuchet @ 3

    Since it doesn’t seem as if methane would be particularly stable on Mars

    Well on Mars it is calculated to naturally decompose into constituents after about 300 years.
    On Earth a decade will see it done and dusted.

    would the presence of methane indicate CURRENT biological processes?

    Well there are several possible sources…Biological…Geological…and ingress by meteorite.

    The latter seems to not provide quite enough for the observed quantity.
    Geologically not likely, because volcanic action along with tectonic activity is the usual sources.
    Mars is structurally a dead clinker…and no geological activity = no methane.

    So that seems to leave biological as prime source, what supports that premise is the seeming cyclical phenomenon that might be related to seasonal temp of vast blooms of the stuff that seems to vanish fairly rapidly and certainly quicker the 300 years.

    Now that observation is an intriguing one because that would indicate that besides a fairly robust source there seems to be an active sink that absorbs the stuff rapidly.
    As far as I am aware there is no known mechanism envisaged to perform this ‘now you see it now you don’t’ scenario!

    Curiosity is equipped to determine the source whatever!

    Or is methane more stable on Mars than on earth?

    Supposed to be but nothing is quite what it seems.

    That is why this revelation that NASA are dangling in front of us is a bit of a poser.

    My take is that it will probably be ‘Organic material’ given that it is supposed to be historic. but I have seen several sites where actual methane is suggested as the find!
    Previous atmospheric samples taken by Curiosity have been virginal in that area at least.

    And noting the various snippets the find was actually in the surface material ingested into SAM at ‘rocknest’…that was presumed to be mainly a sandy particulate, feldspar, olivine and pyroxene constituents in the main…a sand basically.

    But the way I read it the find is in that matrix, if methane then it is vaguely possible it was in ice clumps that the rover scooped up, methane is soluble in water so it could easily be trapped in the ice, but unlikely to be in a gaseous form whatever.
    But there was no announcement made that ice was scooped at all, and I think NASA would have mentioned it, apart from how did they get the icy conglomerate through the filter system into SAM?

    So I got to go logically with ‘Organic material’ other then methane!

    I think they got remnants of biological molecules, or the building blocks of life.
    What intrigues here is that if that is so, it is not likely to be ancient detritus, it is fairly recent.
    Another point if it was scooped up from a modest depth…i.e 4-6 inches under the surface..that is likely to be where a likely habitat for biology would lurk given the surface conditions.

    Thing is Mars is not a logical place, it could well be methane, again stupendous result and just as intriguing, but if biological organics…that raises the real possibility that life is ahem!…alive and well and thriving under the Martian surface, and at a surprisingly shallow depth!

  6. zekehoskin says

    Trebuchet asks: . . .is methane more stable on Mars than on earth?
    Well, the primary things that consume CH4 on earth are oxidation and methanophagic organisms. The main thing that sequesters methane is liquid water.(I’m assuming that icy clathrates froze after the methane got there.) In the absence of much water, free O2 or gas-eating thingies, yes, methane would be more stable on Mars.

    I can’t think of a way to infer current *biological* processes from the existence of methane, but measuring the proportion of C14 in methane will give some notion of whether it was formed recently (from a pool of carbon including recently formed C14) or long in the past (in which case, most of the C14 would have decayed).

  7. anubisprime says

    As zekehoskin has pointed out, the isotopic ratio of light to heavy Carbon is the clue, the lighter species being more associated with biological processes.

    I am not sure there is any other cast iron indicators of biogenic besides that or direct observation of metabolic waste products…basically what they tried to do on the Viking probes in the 80′s…I think they actually scored on both of the labeled release experiments they undertook via the probes.
    But they were unaware that perchlorate’s might have kicked into action by destroying any organics present.
    It was not realized until 2008 that perchlorate’s were part of the Martian chemical zoo.
    That does explain why they got a positive at first, they then heated and they got negatives from then onwards, logical seeing as the perchlorate’s had destroyed any organics by then.

    Curiosity will heat to release constituents but in a manner that does not trigger a perchlorate reaction.

    It might be possible to ‘recognize’ the biological culprit depending on what and how much data they recovered from the analysis.
    Well in so far as they might have enough to work out cellular processes from the organic molecules they actually identify.
    That in itself of course depends on what Organic material was recovered, if indeed recovered it was.

  8. rjlangley says

    A worrying thought just hit this admitted non-scientist…

    …what if Curiosity genuinely had found something organic and alive just below the surface of Mars, but had happened upon the only living organisms on the planet in that one small patch of earth*, wiping out life on Mars in the process? Something akin to an alien visiting a younger Earth and inadvertently destroying the first replicators.

    *on Mars, is the ground still called earth? Or should it be called mars, in lower case?

  9. StevoR says

    Good write up. I love the image of Mars dying and imagine reversing this with terraforming so the sequence goes from red Mars to blue Mars just as in Kim Stanley Robinson’s epic SF trilogy! Of course if Mars does have life currently that’s going to really complicate that possibility if not eliminate it altogether.

  10. says

    A very good question RJ, and I was thinking of writing up a post on a related one after we know if they found anything. Mars is the most ‘terraformable’ planet in our solar system, no other world even comes close in terms of proximity and raw materials to work with. Just small colonies without terraforming would mean inevitable contamination. And while visions of Andromeda Strain are good drama, it’s far likelier that some of the microorganisms on earth, given our vast diversity and their having survived in a sea of competing microbes for billions of years in every kind of climate and eon, would just brush the native Martians aside without even trying. If there are just a few fozen microbes hanging on, or a richer microbial ecology under that red soil, what do we do about it? Because based on what we have done in our own biome, I wouldn’t want to be a Martian.

  11. Trebuchet says

    Got another question. It’s my recollection that amino acids, or their precursors, have been found in meteorites. Any chance of Curiosity having found something of that origin?

    That’s a pretty horrifying but at the top of the post, by the way!

  12. anubisprime says

    Terra-forming Mars is a truly awesome idea, but problem is that what atmosphere it had a few millenia ago has evaporated, presumably into space.


    Well one of the clues is that Mars is not massive enough to hold on to the lighter elements that are not bound in compounds or mineral deposition.
    Add to that the fact that the original molten liquid core of Mars has cooled and solidified…we know it had a molten core because there is ample evidence for volcanic activity and magma flow…some seemingly pyroclastic events are still visible, and resulting flows extend for miles around and form areas reminiscent of Lunar mares!

    The lack of a molten core, that would generate a magnetic sheaf due to field generation which was probably instrumental in the loss of atmosphere and the subsequent drying up of surface liquid water and eventual loss due to disassociation via radiation breakdown.

    To maintain a terraformed planet probably requires at least a mass limit and presumably an active molten core.

    It does not look a particularly viable course at this time, or indeed at near future times.

    Seems the pragmatic course would be to adapt to Martian conditions.
    Engineering and science are seemingly the only tools available.
    It seems eminently unlikely that those tools could render any assistance further then fabricated habitat building in discrete locations.

  13. Dunc says

    Why on Earth (sorry) would you want to terraform anything? It’s got to be several orders of magnitude easier (not to mention quicker) to simply build your own tailor-made space habitat – and that also comes with the added bonus of not having to haul yourself back out of another gravity well to go anywhere else.

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