Earth's doom spelled in collision?

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.

In these cases, its orbit reached an "eccentricity" of 0.6 or more (an eccentricity of zero means the orbit is a perfect circle, while one is the maximum possible elongation). Putting Mercury into such an elongated orbit increases the interactions between Mercury, Venus, Mars and Earth.  

"Once Mercury's eccentricity gets up above about 0.6, then it's getting close to crossing Venus's orbit. Once you get orbit crossings, you sort of transition from the orderly yet chaotic configuration that solar system is in currently to a much more violently chaotic situation. Then all bets are off -- a lot of bad things can happen," Laughlin said.  

Mercury and Mars tend to get thrown around the most when the solar system destabilises, because at six and 11 per cent of Earth's mass, respectively, they are relatively easy to move.  

"In the event of such a collision, Earth is heated to thousands of degrees by the impact, with an ocean of lava covering its surface. A future replay of that event would be disastrous," Laughlin was quoted as saying.  

The studies have been published in the 'Astrophysical Journal'.