Comet impact could make Red Planet inhabitable RT (Russia Today)

A comet near Mars may strike it in a powerful impact, potentially making the planet much warmer. The Red Planet is luring many entrepreneurs, including billionaire Dennis Tito, who aims to beat other nations by sending a man and a woman to Mars.
The make-or-break window for this possible game-changer is October 2014. At that time, an Oort cloud comet called C/2013 A1, first discovered last month, will approach Mars, missing it by about 35,000 km, which is quite close.
However the comet’s trajectory is still uncertain, which leaves a small chance it could impact the planet, said Russian astronomer Leonid Elenin, who worked on calculating the course of the celestial body. The comet will be travelling at a speed of 56 kilometers per second relative to Mars when it passes; if they do collide, the resulting explosion would be equal to a 20,000-gigaton bomb blast – powerful enough to leave a 50-kilometer crater on the planetary surface
The event would trigger a major change of the Martian climate, Australian space scientist Robert Matson explained. The impact would evaporate large amounts of water and carbon dioxide ice from the comet, spread across a planetary scale, making the climate on Mars much warmer due to the greenhouse effect.