Somebody should get ahold of Earl Kyle if possible. Comet Siding Spring 2013 A1 will pass within 65,000 miles of Mars in October 2014 and currently has a 1 in 10,000 chance of hitting the planet.
If it does, the nucleus is estimated to be 30 to 40 miles across. That would mean a BIG hole in the Red Planet.
More info is available on the Sky&Telescope website.