Assessing the habitability of Mars and detecting life, if it was ever there, depends on knowledge
of whether the combined environmental stresses experienced on Mars are compatible with life
and whether a record of that life could ever be detected. Many combinations of Mars relevant
stress factors, such as high radiation dose rates and high UV
uences combined with high salt
concentrations, and low water activity, have not been investigated. In particular, the response
of anaerobic organisms to Mars-like stress factors and combinations thereof are not known. In
the EC project MASE (Mars Analogues for Space Exploration) we address these limitations by
characterising different Mars analogue environments on Earth, isolating microorganisms from
these sites and exposing them to Mars relevant stress factors alone and in combination. We
want to find out, if these bacteria respond in an additive or synergistic way and if they would
be able to survive on Mars. So far, eight only distantly related microorganisms are under
detailed investigation, e.g Yersinia sp., Halanaerobium sp., Acidiphilum sp. Desulfovibrio sp..
Unexpectedly, a Yersinia strain turned out to be quite resistant, especially against desicca-
tion and oxidising compounds, whereas a Desulfovibrio sp. strain exhibit a relatively high
radiation resistance. The future experiments aim at the identification of the underlying cellu-
lar and molecular mechanisms and the comparison to other new isolates from Mars analogue
environments on Earth in the MASE project
