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Contaminating other planets is a concern in space exploration. My question is what organisms, or small collections of organisms, from earth would be able form a self-sustaining population on Mars? I'm not worried about how they might get there, so deep sea microbes and the like which would have to be purposely transported are in scope.

This is not the same as this earlier question, as that one does not consider sustainability.

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  • $\begingroup$ Tardigrades would certainly make it, at least for a while... $\endgroup$ – honeste_vivere Aug 3 '16 at 12:38
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On the surface of Mars probably none, since it's too dry or too cold, or both, to stay active.

Spores or other dormant forms probably could survive for centuries, until radiation will gradually destroy the organic molecules necessary to get back into an active state.

But there are "Mars Special Regions", where either Earth microbes or potential Martian microbes - if some exist - cannot be ruled out to be able to spread.

Things might look quite different in the underground, especially in warm and wet zones, which may exist by geothermal heat and ground water. There, at least lithotrophic bacteria/"chemolithoautotrophs" could survive and spread. Those could then form a basis for a food chain of other organisms.

Plants dependent on sunlight, or animals dependent on oxygen would hardly survive.

For a list of species, see table 2 on page 895 of the above reference paper. The following species and genera are mentioned in the table: Psychromonas ingrahamii, Planococcus halocryophilus strain Or1, Paenisporoarcina sp. and Chryseobacterium, Rhodotorula glutinis (yeast), Colwellia psychroerythraea, Nitrosomonas cryotolerans, (lichen) Pleopsidium chlorophanum.

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I don't think there is necessarily a problem with it being dry or cold. An excellent similacrum of the Martian surface conditions is found in Antarctica. There are plenty of anaerobic microbes that exist here. A brief search reveals Shivaji (1988); Franzmann & Rhode (1992); Dube et al. (2001).

To quote the wikipedia entry on the "McMurdo dry valleys" - "Endolithic photosynthetic bacteria have been found living in the Dry Valleys, sheltered from the dry air in the relatively moist interior of rocks. Summer meltwater from the glaciers provides the primary source of soil nutrients. Scientists consider the Dry Valleys perhaps the closest of any terrestrial environment to the planet Mars, and thus an important source of insights into possible extraterrestrial life." I think that's quite direct.

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