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The question of whether present-day Mars could be habitable, and to what extent, has been the focus of long-running and intense debates. The surface, comparable to the dry valleys of Antarctica and the Atacama desert on Earth, is harsh, with well-below freezing temperatures most of the time (at an average of minus 63 degrees Celsius or minus 81 Fahrenheit), extreme dryness and a very thin atmosphere offering little protection from the Sun’s ultraviolet radiation. Most scientists would agree that the best place that any organisms could hope to survive and flourish would be underground. Now, a new study says that scenario is not only correct, but that large regions of Mars’ subsurface could be even more sustainable for life than previously thought.
Scientists from the Australian National University modeled conditions on Mars on a global scale and found that large regions could be capable of sustaining life – three percent of the planet actually, albeit mostly underground. By comparison, just one percent of Earth’s volume, from the central core to the upper atmosphere, is inhabited by some kind of life. They compared pressure and temperature conditions on Earth to those of Mars to come up with the surprising results.
According to Charley Lineweaver of ANU, “What we tried to do, simply, was take almost all of the information we could and put it together and say ‘is the big picture consistent with there being life on Mars?’ And the simple answer is yes… There are large regions of Mars that are compatible with terrestrial life.”
So it seems that while, as we know, the surface of Mars is quite inhospitable to most forms of life (that we know of) except perhaps for some extremophiles, conditions underground are a different matter. It is already known that there are vast deposits of ice below the surface even near the equator (as well as the polar ice caps of course), so there could be liquid water a bit deeper where it is warmer. Those conditions would be ideal for bacteria or other simple organisms. While that idea has been proposed and discussed before, Lineweaver’s findings support it on a planet-wide basis – previous studies tended to focus on specific locations in a “piecemeal” approach, but these new ones take the entire planet into consideration.
The paper is currently available for free here. Abstract:
We present a comprehensive model of martian pressure-temperature (P-T) phase space and compare it with that of Earth. Martian P-T conditions compatible with liquid water extend to a depth of *310 km. We use our phase space model of Mars and of terrestrial life to estimate the depths and extent of the water on Mars that is habitable for terrestrial life. We find an extensive overlap between inhabited terrestrial phase space and martian phase space. The lower martian surface temperatures and shallower martian geotherm suggest that, if there is a hot deep biosphere on Mars, it could extend 7 times deeper than the *5km depth of the hot deep terrestrial biosphere in the crust inhabited by hyperthermophilic chemolithotrophs. This corresponds to *3.2% of the volume of present-day Mars being potentially habitable for terrestrial-like life. Key Words: Biosphere—Mars— Limits of life—Extremophiles—Water. Astrobiology 11, xxx–xxx.