When I first heard this story on the radio, I had to check the calender to see if it was April First, but it is a real story.
A comet was discovered early last year coming up from below the plane of the ecliptic. It is named after the Siding Spring Observatory in Australia where it was spotted in a 20 inch scope.
It is expected to pass Mars at a distance of 132,000 kilometers on October 19th. For scale, that is about a third of the distance from the Earth to the Moon. No comet has ever been recorded coming that close to the Earth.
After this near-miss (George Carlin would say, near-hit), Mars will pass through the dust tail of the comet 90 minutes later. NASA and JPL want their satellites to be on the other side of Mars when this happens.
http://mars.nasa.gov/comets/sidingspring/ http://news.sciencemag.org/physics/2014/07/comet-fireworks-mars http://mars.nasa.gov/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=... http://www.jpl.nasa.gov/news/news.php?release=2014-244