An experiment using Siberian permafrost methanogenic archaea showed that 90% of the archaea have the ability to survive Martian conditions.

Methanogens from Siberian permafrost were exposed to Mars-like conditions over a period of 22 days and 90% of the Siberian archaea survived, compared to archaea from other environments. While the paper does not necessarily claim that similar archaea live at the sub-surface on Mars, it does suggest that if life does exist there, it is possible for it to somewhat resemble these methanogenic archaea. If similar methanogenic cells exist on Mars, they could be responsible for the methane fluctuations measured in the Martian atmosphere.

Authors

Möhlmann, D., Morozova, D., and Wagner, D.

Abstract

Methanogenic archaea from Siberian permafrost complementary to the already well-studied methanogens from non-permafrost habitats were exposed to simulated Martian conditions. After 22 days of exposure to thermo-physical conditions at Martian low- and mid-latitudes up to 90% of methanogenic archaea from Siberian permafrost survived in pure cultures as well as in environmental samples. In contrast, only 0.3%-5.8% of reference organisms from non-permafrost habitats survived at these conditions. This suggests that methanogens from terrestrial permafrost seem to be remarkably resistant to Martian conditions. Our data also suggest that in scenario of subsurface lithoautotrophic life on Mars, methanogenic archaea from Siberian permafrost could be used as appropriate candidates for the microbial life on Mars.

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Methanogens can survive in desert regolith on Earth analogous to those found on Mars and therefore have the resources they need to produce methane in a Martian environment.

This paper discusses experiments done with methanogenic life in different environmental conditions. Methanogens were found to best survive in swamp-like conditions. However, they could still survive in desert conditions analogous to those on Mars, essentially in warmer, non-permafrost regions. Methanogens living in desert regolith could help explain the methane fluctuations seen in the Martian atmosphere since the regolith has the resources the methanogens need to survive and produce methane.

Authors

Kral, T., Miller, J.D., Moran, M., Scott, D.

Abstract

Methane, a potential biosignature, has recently been detected in the martian atmosphere. This Note focuses on field investigations/operational simulations and laboratory studies which resulted in successful detection of methane within arid terrestrial soils, as distinct from the usual methanogen environment, but in at least partial analogy to martian conditions.

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Certain strains of methanogens in one experiment grew in JSC Mars-1 soil with carbon dioxide, hydrogen,and varying amounts of water.

An experiment was conducted using four different strains of methanogens to see how they would survive in Martian soil. They were put in an environment with carbon dioxide, hydrogen, and different amounts of water, while being subjected to other Martian environmental conditions. Three of the strains were able to grow under the given conditions, giving rise to the possibility that such species could thrive on Mars. While it does not mean they exist on Mars, if species are found in the soil in the future, they would perhaps resemble these tested methanogens.

Authors

Bekkum, C. R., Kral, T. A., and Mckay, C. P.

Abstract

Currently, the surface of Mars is probably too cold, too dry, and too oxidizing for life, as we know it, to exist. But the subsurface is another matter. Life forms that might exist below the surface could not obtain their energy from photosynthesis, but rather they would have to utilize chemical energy. Methanogens are one type of microorganism that might be able to survive below the surface of Mars. A potential habitat for existence of methanogens on Mars might be a geothermal source of hydrogen, possibly due to volcanic or hydrothermal activity, or the reaction of basalt and anaerobic water, carbon dioxide, which is abundant in the martian atmosphere, and of course, subsurface liquid water. We report here that certain methanogens can grow on a Mars soil simulant when supplied with carbon dioxide, molecular hydrogen, and varying amounts of water.

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No significant source of abiotic methanogenesis has been found.

This paper discusses geological and cosmochemical abiotic processes that could possibly produce or remove methane. These include volcano activity, deep hydrothermal vent activities, and meteorites carrying molecules that can combine with other particles to produce methane. An analysis of all the different processes shows that none of them can significantly contribute to the magnitude of methane variations in the atmosphere. While this paper does not claim that biotic processes are causing changes in methane levels, it does not rule out the possibility, since the most likely sources of methane on Mars do not come anywhere near close to producing all the methane fluctuations that are seen.

Authors

Krasnopolsky V.A., Maillard, J.P., and Owen, T.C.

Abstract

Using the Fourier Transform Spectrometer at the Canada–France–Hawaii Telescope, we observed a spectrum of Mars at the P-branch of the strongest CH4 band at 3.3 μm with resolving power of 180,000 for the apodized spectrum. Summing up the spectral intervals at the expected positions of the 15 strongest Doppler-shifted martian lines, we detected the absorption by martian methane at a 3.7 sigma level which is exactly centered in the summed spectrum. The observed CH4 mixing ratio is 10 +/- 3ppb. Total photochemical loss of CH4 in the martian atmosphere is equal to 2.2 x 10^5 cm^-2 s^-1, the CH4 lifetime is 340 years and methane should be uniformly mixed in the atmosphere. Heterogeneous loss of atmospheric methane is probably negligible, while the sink of CH4 during its diffusion through the regolith may be significant. There are no processes of CH4 formation in the atmosphere, so the photochemical loss must therefore be balanced by abiogenic and biogenic sources. Outgassing from Mars is weak, the latest volcanism is at least 10 million years old, and thermal emission imaging from the Mars Odyssey orbiter does not reveal any hot spots on Mars. Hydrothermal systems can hardly be warmer than the room temperature at which production of methane is very low in terrestrial waters. Therefore a significant production of hydrothermal and magmatic methane is not very likely on Mars. The calculated average production of CH4 by cometary impacts is 2% of the methane loss. Production of methane by meteorites and interplanetary dust does not exceed 4% of the methane loss. Methane cannot originate from an extinct biosphere, as in the case of “natural gas” on Earth, given the exceedingly low limits on organic matter set by the Viking landers and the dry recent history which has been extremely hostile to the macroscopic life needed to generate the gas. Therefore, methanogenesis by living subterranean organisms is a plausible explanation for this discovery. Our estimates of the biomass and its production using the measured CH4 abundance show that the martian biota may be extremely scarce and Mars may be generally sterile except for some oases.

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Methane is disappearing at a faster pace than other trace gases in the Martian atmosphere by unknown processes, indicating that a factor at the sub-surface is responsible for methane fluctuations.

The paper discusses the findings of variations in methane in the Martian atmosphere and investigates possible photochemical and atmospheric causes for the fluctuations. Atmospheric effects may cause some fluctuations, but the rate of methane loss atmospheric processes would cause is inconsistent with observed rates. Photochemical processes do not cause much variation in methane levels as well, so they certainly do not cause such a large rate of methane loss either. This paper suggests that life could be a factor in methane fluctuations on Mars, as there is an unidentifiable sink that is causing a rapid decrease in methane levels at times, considering that methane loss happens at a rate up to 600 times faster than photochemical processes can destroy it. There still could be a more significant abiotic process at play, but it does not rule out the possibility for life being involved.

Authors

Lefevre, F., and Forget, F.

Abstract

The detection of methane on Mars has revived the possibility of past or extant life on this planet, despite the fact that an abiogenic origin is thought to be equally plausible. An intriguing aspect of the recent observations of methane on Mars is that methane concentrations appear to be locally enhanced and change with the seasons. However, methane has a photochemical lifetime of several centuries, and is therefore expected to have a spatially uniform distribution on the planet. Here we use a global climate model of Mars with coupled chemistry to examine the implications of the recently observed variations of Martian methane for our understanding of the chemistry of methane. We find that photochemistry as currently understood does not produce measurable variations in methane concentrations, even in the case of a current, local and episodic methane release. In contrast, we find that the condensation-sublimation cycle of Mars' carbon dioxide atmosphere can generate large-scale methane variations differing from those observed. In order to reproduce local methane enhancements similar to those recently reported, we show that an atmospheric lifetime of less than 200 days is necessary, even if a local source of methane is only active around the time of the observation itself. This implies an unidentified methane loss process that is 600 times faster than predicted by standard photochemistry. The existence of such a fast loss in the Martian atmosphere is difficult to reconcile with the observed distribution of other trace gas species. In the case of a destruction mechanism only active at the surface of Mars, destruction of methane must occur with an even shorter timescale of the order of approximately 1 hour to explain the observations. If recent observations of spatial and temporal variations of methane are confirmed, this would suggest an extraordinarily harsh environment for the survival of organics on the planet.

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