Is there life on Mars? A group of Canberra scientists says it's possible.
The scientists, based at the Australian National University, say extensive areas of the subsurface of Mars may contain water at a comfortable temperatures for microbes.
The scientists had previously modelled the Earth and identified water which was inhabited and other water which was not. They used the same technique to model Mars and were surprised to find the results showed more water than they were expecting.
''Our models tell us that if there is water present in the Martian sub-surface then it could be habitable, as an extensive region of the subsurface is at temperatures and pressures comfortable for terrestrial life,'' the study's lead author, PhD student Eriita Jones said.
The team found about 3 per cent of the volume of present-day Mars has the potential to be habitable to terrestrial-like life.
This compares with only about 1 per cent of the entire volume of the Earth being inhabited.
''We know that there is a hot, deep biosphere on Earth that extends to around 5km,'' co-author of the paper Charley Lineweaver said.
''If there is a hot deep biosphere on Mars, our modelling shows that it could extend to around 30km.''
However, the scientists are disappointed that the next space mission to Mars is not expected to make much progress on their theories. ''Our conclusion is that the best way to find water, or potentially microbes, on Mars is to dig,'' Dr Lineweaver said.
''Sadly, NASA's Curiosity Rover, which is scheduled to land on Mars in August, has a limited capacity to scratch the surface 10 or 20cm,'' he said.