The best place to look for life on Mars and other planets could be the impact craters of asteroids.
Scientists at the University of Edinburgh say they've discovered microbes thriving deep beneath a US site where an asteroid crashed some 35 million years ago.
They say it's evidence that such craters can provide refuge for such organisms, sheltering them from everything from the weather to events such as global warming or ice ages.
"The deeply fractured areas around impact craters can provide a safe haven in which microbes can flourish for long periods of time," says Professor Charles Cockell of the university's School of Physics and Astronomy.
"Our findings suggest that the subsurface of craters on Mars might be a promising place to search for evidence of life."
Cockell's team drilled almost 2km below one of the largest asteroid impact craters on Earth, in Chesapeake, US.
Samples from below ground showed that microbes are unevenly spread throughout the rock - suggesting that the environment is continuing to settle 35 million years after impact, they say.
While the heat from the impact of an asteroid collision would kill everything at the surface, says Cockell, fractures to rocks deep below would enable water and nutrients to flow in and support life.