New York (PTI): No one knows exactly how life on Earth will end. But scientists claim that a collision with Mercury or Mars could destroy our planet long before the Sun bakes it to a crisp in five billion years' time.

Two separate studies suggest that the solar system's planets will continue to orbit the Sun stably for at least 40 million years. But after that, there's a chance that Mercury's orbit will get out of whack in the next five billion years.

This would tend to destabilise the whole inner solar system and could lead to a catastrophic collision between Earth and either Mercury or Mars, wiping out any life still present at that time, the studies claim.

"In the case of a smash up with Mars, all life gets extinguished immediately, and Earth glows at the temperature of a red giant star for about 1,000 years," Gregory Laughlin, the author of one of the studies at California University, was quoted by the 'New Scientist' as saying.

In the other study, Jacques Laskar at the Observatoire de Paris in France ran 1,001 computer simulations of the solar system over time, which revealed that in one to two per cent of the cases, Mercury's orbit became very elongated over time due to gravitational tugs by Jupiter.