If there is life on Mars it may be lurking in craters formed by asteroid impacts on the planet's surface, as has happened on Earth, Scottish scientists say.

Researchers at the University of Edinburgh said organisms have been found living deep beneath a site in Chesapeake Bay in the United States where an asteroid crashed 35 million years ago, suggesting crater sites on other planets may be "hiding life."

Heat from such impacts would kill everything at the surface but fractures leading to rocks deep below could allow water and nutrients to flow in and support life.

"The deeply fractured areas around the impact craters can provide a safe haven in which microbes can flourish for long periods of time," researcher Charles Cockrell told the BBC.

Craters may provide shelter to microbes, shielding them from the effects of changing seasons and catastrophic events such as global warming or ice ages, he said.

"Our findings suggest that the subsurface of craters on Mars might be a promising place to search for evidence of life," he said.