Australian scientists who modeled conditions on Mars to examine how much of the red planet was habitable said on Monday that "large regions" could sustain life.

Charley Lineweaver's team, from the Australian National University (ANU), compared models of temperature and pressure conditions on Earth with those on Mars to estimate how much of the distant planet was livable for Earth-like organisms.

While just 1 percent of Earth's volume - from core to upper atmosphere - was occupied by life, Lineweaver said their world-first modeling showed 3 percent of Mars was habitable, though most of it was underground.

"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?'," the astrobiologist said.

"And the simple answer is yes ... There are large regions of Mars that are compatible with terrestrial life."

Where previous studies had taken a "piecemeal" approach by examining particular sites on Mars for signs of life, Lineweaver said his research was a "comprehensive compilation" of the entire planet using decades of data.

Frozen water has been found at the poles on Mars and the ANU study examined how much of the planet could sustain water "that could be habitable by Earth-like standards by Earth-like microbes".

The low-pressure environment of Mars means water cannot exist as a liquid and will vaporize on the surface, but Lineweaver said the conditions are right underground, where the weight of the soil gives the added pressure required.

It would also be warm enough, at certain depths, for bacteria and other micro-organisms to thrive due to heat from the planet's core.

The average surface temperature on Mars, Earth's nearest neighbor, is minus 63 C.

Lineweaver said his study was "the best estimate yet published of how habitable Mars is to terrestrial microbes" and a significant finding given mankind had evolved from microbial life.

"It's not important if you want to figure out what the laws of physics are and you want to talk to some intelligent aliens who could build spaceships," he said.

"If you're interested in the origin of life and how likely life is to get started on other planets, that's what relevant here."

NASA's Curiosity Rover, the largest, most sophisticated robotic explorer ever built, is en route to Mars and due to land in August 2012.

It has a laser beam for zapping rocks and a tool kit to analyze their contents as well as a robotic arm, drill, cameras and sensors to enable it to report back on the Martian weather and atmospheric radiation.