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The Indirect Case For Life On Mars
Deinhard writes "Space.com is reporting that '[a] pair of NASA scientists told a group of space officials at a private meeting here Sunday that they have found strong evidence that life may exist today on Mars, hidden away in caves and sustained by pockets of water.' It is all based on methane signatures and not direct observation. Now plans for using the Genesis Device on Mars are out ... unless this is just a particle of preanimate matter caught in the matrix."
If ancient life can be discovered under Antarctic ice, nothing is unpossible.
Given our accessibility and coverage on earth, we didn't know about this ancient life until recently.
And now we only have few rovers on Mars...
Rock that crushes, Paper & Scissors that don't matter.
According to http://www.newscientist.com/article.ns?id=dn7014 the scientists have not only detected methane, but also formaldehyde, which was measured at levels of 130 parts per billion. From the article:
He thinks that the gas is being produced by the oxidation of methane and estimates that 2.5 million tonnes of methane per year are needed to produce it. "I believe that until it is demonstrated that non-biological processes can produce this, possibly the only way to produce so much methane is life," he says. "My conclusion is there must be life in the soil of Mars."
Bruce
I think it's the significant temporal VARIATION of methane content in the atmosphere of Mars that is peaking interest in this theory, not just the presence ot methane.
Evidence of methane and its coverage with water can be expained in at least one trivial way. Note Mars atmospheric composition:
C02: 95%
H2O: 0.03%
Now huge ultraviolet radiation breaks down H2O and CO2 to loose hydrogen/oxygen/carbon atoms (this process along with mars weak gravity is co-responsible for mars losing its once dense atmosphere). Additionally there is huge evidence of Electrical Discharge On The Martian Surface
Try simple high school science project: Load a container with water and CO2, add electrodes to create some discharge ('lightning') and you'll have your own PanGea in a bottle.
After some time all sorts of 'organic' chemicals will be present in the bottle along with most common methane (but also alcohols, higher carbohydrates and more complex molecules). I would think decent scientist would at least mention such possibility in reocurring articles on 'OH-OH methane is evidence of life on mars'
Actually, the deal with the methane is this:
Its lifetime in the atmosphere is ~ 350 (earth) years. Thus, for the amount of methane detected, either there was recent (years ago, not Ma or even Ka) volcanic activity, or there is life currently producing the methane. Either of these two speculations is valid.
Your other suggestions are valid also, but require something to help them release their trapped methane. Ices/clathrates need to be melted, which means they need energy input. Hydrocarbon deposits would require life to have existed in the past, and would require something to release just the methane form rather than a bunch of other stuff. i.e., we would see other (than just methane) evidence for a degassing hydrocarbon resevoir.
The volcanism argument is very difficult to sustain because we don't see evidence for it NOW (however, as my advisor is always looking for opportunities to point out, "absence of evidence is not evidence of absence."). I like the volcanism argument because I like volcanism, but the most recent flow fields are 10 Ma, and seem to have been the last gasp of a dying planet. Unless they released a LOT of methane into the atmosphere, the current methane is not from those flows.
The life argument has some major problems, but it's at least worth investigating. There needs to be some sort of energy to maintain these putative methanogens, and that's one of the issues right now (we don't know where to look for life because we don't see any* evidence for subsurface energy).
We can't directly look for concentrations of methane because the in situ measurements would provide something like 1 PPM, and averaged through the atmosphere would be undetectably low compared with the amount of the methane in the (presumed well-mixed) atmosphere (ppb).
* There are small east-west trending fissures (canyons) that may be the best places to search for life-sustaining energy because they collect daytime sunlight but don't effeciently reemit it at night, thus increasing their temperatures relative to the surroundings and possibly conducting heat to the subsurface and possibly collecting enough heat to sustain life. . . I'll let you know in a week or so if this pans out. . .
...what if we brought life to mars?
Those who know, do not speak. Those who speak, do not know. ~Lao Tzu