After the passage of the asteroid 2012-DA14 near the Earth, Mars could know the same think, but with a comet, called C/2013 A1.
It's Robert H. McNaught, australian astronomer at Siding Spring Observatory, who has discovered this comet on January 3rd 2013. Just after this discover, the first calculations showed that C/2013 A1 would be near of Mars at more than 100,000 km.
But the last estimates showed a distance of 37,000 km, with a 190,000 km/h speed (according to the Daily Mail) and a diameter between 15 and 50 km. The date announced for this passage near Mars is October 19th 2014. Further, the comet will be near of the sun one week later (October 25th).
If C/2013 A1 crash on Mars, a crater of more than 500 km in diameter could be form and create a great cataclysm. Astronomers must wait march 2014 to have more accurate data about the comet, and check if, yes or no, the comet will crash on the red planet. It will be the duty of Curiosity and Opportunity rovers, with Mars Reconnaissance Orbiter (MRO) to give us next year more info about the comet.