I'm working on my own analysis of the comet's orbit and the potential risk right now, but in the meantime since word is starting to get around about this I wanted to go ahead and make the thread to put this out there. Hat tip to Dr. Ian Musgrave:
[link to astroblogger.blogspot.com]
Now, it's important to point out that we don't know the orbit well enough yet to know if it will hit or not. It could make a very close pass to Mars, or it could collide. We just don't know yet. I'm currently running my own analysis to try to determine the level of risk. If it hits though (which would be on October 19th, 2014), the impact will be tremendous. This comet is on a retrograde orbit, traveling the opposite direction of the planets, so a head-on collision would be in excess of 50 km/sec. That's very, very high. Minimum distance of the approach is currently sitting at 0 on JPL's site, maximum distance is at 0.00794 AU.
[link to ssd.jpl.nasa.gov]
It would be a very, very bad day to be a martian if this thing hits.