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http://spaceobs.org/en/2013/02/27/ne...13-a1-to-mars/
http://www.planetary.org/blogs/emily...past-mars.html
http://ssd.jpl.nasa.gov/sbdb.cgi?sst...ov=0;log=0#cad

The most recent measurements of comet C/2013A1's orbit show it will pass roughly 37,000 km from the surface of Mars next year. Uncertainty of the orbit still leaves a small chance of a direct impact.

That's a little bit farther out than asteroid 2012DA14 passed from Earth, but this comet is much larger. But, A1s coma should be ~100,000 km in diameter by the time it reaches Mars's orbit.

Even if the nucleus does not impact, Mars will still be passing through the coma and be subjected to some degree of bombardment, including objects large enough to pass through the Martian atmosphere and pose a danger to probes in orbit and on the surface - we don't know how dense the meteor rain from a coma passage like this would be.

If the probes survive, it's hoped they'll be able to get images of the comet as it passes, since it'll dominate the sky for several days and completely fill it at closest approach.

In the event of an actual direct impact, probes on the surface will almost certainly be lost. The current size estimate range is 15-50km. At 15 km it'd already be one of the largest comets to pass through the inner solar system, and at 50 km it'd be second only to Hale-Bopp.

Last edited by hevach; 02-28-2013 at 01:01 PM.