Astronomers have been peering at the sky for clues (Parkes radio telescope pictured) that there may be alien life forms on other planets for decades, but a new theory suggests that in the majority of cases, life would have died out quickly after appearing on a planet as it was not able to alter the climate of its world enough to survive
And they said that while many planets could have potentially been habitable, and may have once teemed with microbial life, runaway heating or cooling would have left their surfaces inhospitable.
In their new theory, the researchers looked at the role life can play in helping to control the climate of a planet, making it more habitable in the process.
They argue that while both Mars and Venus may once have been planets that could have hosted life four billion years ago, any life there failed to stabilise the environment.
The researchers, based at the Australian National University, argue that life may well have emerged multiple times on other planets following the heavy bombardment of wet rocky worlds by asteroids.