Comet C2013 A1 was discovered on January 3, 2013 by Robert McNaught at Siding Spring Observatory. Believed to have been thrown from the Oort cloud; this one is poised to give Mars a little trouble. On October 29, 2014 estimates place it within 37,000 Km. from the surface of Mars.
A lot can happen to this projection in the next year. This isn’t a single asteroid, rather a massive comet with a nucleus estimated anywhere from 15 to 50 Km, and a tail up to 100,000 Km. This tail isn’t just along for the ride; it’s made up of smaller rubble and frozen gasses – often with a mind of their own. C2013 A1 is passing close enough to the Sun at the moment to melt some of these frozen gasses, sending them hurtling into space. Often this action is enough to change the course of a comet, though best guesses are placing money on a close call rather than a direct hit.
Mars may be spared an impact estimated at 25 million times more powerful than a nuclear bomb – it has no chance of escaping the massive tail. Without question it will be spanked by unknown quantities of space junk.
There is no chance that Earth will be in harms way. At least not this time around.