Found this interesting article about a temporary belt discovered by scientists last year. http://science.nbcnews.com/_news/2013/02/28/17134882-new-radiation-belt-arou... BTW, if by some miracle that comet does hit Mars, let's hope it hits on the Earth facing side! It it was to hit along the rim (from our point of view) I'd presume it could make for a very interesting dust plume?! Tom Sevcik