Thirty two years ago, Viking landers conducted three experiments to test for life on the surface of Mars, the results were inconclusive.
The gas exchanger (GEX) experiment attempted to detect changes of the makeup of gases in a test tube indicative of biological experiments.
The labeled release (LR) experiment provided radioactively labeled nutrients for biological organisms and then detected gases emitted by these organisms.
The pyrolytic release (PR) experiment attempted to detect the uptake of radioactive carbon by cooking it out of potential organisms.
For these experiments there was also a control in which the soil was first precooked at 320F to sterilize it. If the sterilized control sample produced the same test results, non-biological activity must be responsible.
The GEX and PR experiments provided positive results, but the control experiment was also positive indicating some non-biological process was at work.
The LR experiment provided positive results for the non-sterilized sample but not for the sterilized sample. When the labeled nutrients were first injected there was a rapid release of labeled gas, but subsequent injections of nutrients caused an initial decrease followed by a slow rise. The decrease was unexpected causing the results to be interpreted as ambiguous.
It was believed that the experiments were the result of unusual soil chemistry involving super oxides and materials which could catalyze some of these results. The exact chemical reactions that could explain these results are unknown. There are life forms that utilize a mixture of water and hydrogen peroxide, H2O2 in their cellular fluids which could produce exactly the results seen in the Viking life experiments. On Earth the soil bacterium Acetobacter Peroxidans is such an example. This article on Mars Daily provides additional details.
The Phoenix lander did not find unusual soil chemistry. The soil it found would be friendly to life, so much so that they say you could grow asparagus in it (but not strawberries because it is somewhat alkaline).
In 2004, Methane and Ammonia were detected in the atmosphere of Mars. Because methane and ammonia are not stable in the Martian environment, something has to be replenishing it. Known mechanisms are either volcanism or biological processes. No active volcanoes have been detected on Mars. In 2005, Vittorio Formisano, chief scientists for the ESA Mars Express Planetary Fourier Spectrometer, found formaldehyde in the martian atmosphere at levels that he believes are too great to be explained by volcanic origin.
Rather than being omnipresent, life may exist in discrete niches on the surface of Mars where atmospheric pressure is unusually high allowing liquid water to exist during the warm season. The average atmospheric pressure is between 6-9 millibars depending upon the season but may approach 10 millibars in low lying locations.
At 10 millibars, the boiling point of water is 45F, so in the depths of some of the craters and trenches there is the potential for liquid water to exist for at least part of the Martian year. Phoenix also found a salt in the soil and this would extend the temperature window over which water may remain a liquid.
What the Phoenix lander failed to find in the Martian soil is fixed nitrogen and organic carbon compounds. On Earth, there are some bacteria capable of fixing nitrogen from the atmosphere and some which are capable of photosynthesis. The Martian atmosphere is only about 3% nitrogen but this may be sufficient for properly adapted microbes.
The argument is also made that high levels of UV light would sterilize the surface, however, bacteria present on the surface of equipment we left on the moon were found to be viable after being exposed to direct sunlight in the lunar environment for a year and since our moon is closer to the Sun than Mars and has no atmosphere at all, the UV levels reaching the surface are even higher than on Mars.
Bacteria in nuclear reactors have evolved that survive high levels of neutron and gamma radiation and have even evolved a form of melanin that can absorb and utilize energy present in gamma rays for the organisms energy needs.
It is not inconceivable that organisms on Mars may have evolved with pigments capable of protecting them from UV radiation and even utilize this energy for their own biological purposes.
Based upon this conjecture, I searched ESA photographs from Mars Express of locations below average terrain elevation, having the potential for liquid water, for anything which may be of biological origin and found items of interest.
Note the dark coloration tends to diffuse out of a central area but does not correspond directly with geological objects, rather it tends to flow over everything but only below a certain critical depth.
Here in Mamers Valles we see a similar discoloration, and again, it seems to flow out from the center rather than being blasted and splattered, with diffuse but fairly well defined borders.
This sure looks like a colony of something. It has a strong resemblance the things grown on bread that I’ve left sitting too long in the cupboard. Nasa describes these features as Barchan dunes, but that doesn’t explain why they are so sharply contrasted in color to surrounding features. Gullies along the upper side of the trough in the center of the crater are believed to have been caused by liquid water.
The hairs or filamentary structures present are interesting. I believe I heard someone from NASA suggest these were dust devil trails while totally neglecting to indicate why they only formed over the dark material and did not displace the lighter material in a similar manner. I suppose it could be argued that the darker material absorbed more sunlight and provided more heat for the formation of dust devils. The material has the appearance of something biological in nature even if dust devils distributed it.
I have lightened this image considerably because in it’s original form the dark material was so dark that detail below it was obscured and you couldn’t see the apparent flow and variability in color and saturation. Note how the flow seems to be semi-radial outward from the center rather than linear as one might expect if this were simply wind blown dark material. This resembles more an organism arising at one spot and them propagating outward.
The colors here suggest multiple colonies of different organisms with quite different pigments. The patterns of rocks to the lower right look like something in a flood plain where mud has washed up around them. The thickest deposits of pigmented material appears to center around a crack in the crust. Perhaps there are nutrients or organisms that were brought up from depths at this location. It’s impossible to eliminate some interesting non-biological chemistry here but it sure reminds me of some of the colorful bacterial colonies around Yellowstone hot springs. Those bacteria are thermophiles that are adapted to hot water but the patterns seem very similar.
Hebes Chasma is extremely interesting anyway you want to look at it. There is no inflow or outflow, no surrounding debris field. Where did this chunk of crust go? The feature in the center also is raised. The presence of the central plateau is unique to this structure. This is about 8000 meters deep.
I believe there is a combination of mineral and biological processes responsible for the pigmentation in this structure. You can see some pigments follow geological structure very cleanly, but others appear to be a more diffuse substance overlying multiple structures.
The 8000 meter depth would allow for higher pressures which in turn would allow for water to remain liquid. The reflection off of the walls would tend to amplify heat and the dark pigments would also tend to capture more of the suns energy resulting in warmer temperatures conducive to liquid water.
This looks more like a terraced Chinese rice field than something you would expect to find on Mars. The terraced walls suggests erosion of sedimentary rock, but for sedimentary rock to form on that scale would require huge amounts of water over a long period of time. Or maybe it’s an alien strip-mine.
What actually caught my interest is the green area near the bottom of the image. It bears a strong resemblance to the algae growth.
And I’ll close with this image cropped from a frozen lake in a Martian crater. This is cropped from a much larger image to show a feature at the north end of the frozen lake where it appears to me to be partially thawed, and where it appears dark blue green colonies of something are growing at the borders. There also appears to be some lighter greenish colonies of something on or below the ice.
That’s my case for life on the surface of Mars.