I have been doing some calculations in regards to an asteroid named (4179) Toutatis. It appears to have a very close intersection with Earth on mid-December 2012. Are you able to detemine with more accuracy how close this asteroid will come to Earth and what chances that it will make contact? AND Comet 45p/honda-mrkos is due to pass within 0.06 AU in 2011. I keep reading about this comet’s erratic orbits. This would appear to be a very close visit by a comet; what are the risks from debris/radiation/flares/asteroids?

While the Earth is subject to rare impacts by comets and asteroids, there are no predictions of any impacts in this century (see the NASA impact hazard website at http://impact.arc.nasa.gov). Concerning asteroid Toutatis, the orbit is very well known because this asteroid has been tracked by radar as well as optical telescopes. You don’t need to do your own orbit calculations, since current orbital information for all near-Earth asteroids is posted on the NASA NEO Program website at http://neo.jpl.nasa.gov. The next close approach by Toutatis is on December 12, 2012, at a distance of 0.046 Astronomical Units (AU), or about 18 times the distance of the Moon. This miss is by a wide margin, with zero probability of its affecting Earth. The 2011 flyby distance of Comet Honda/Mrkos is even greater. There is no risk from debris/radiation/flares/asteroids; comets don’t produce radiation or flares, and they are not accompanied by asteroids. A comet does have an atmosphere and dust that is released from the surface as it is heated by the Sun, but none of this material would hurt the Earth even if we passed right through the tail. For a good introduction to comets see Wikipedia at http://en.wikipedia.org/wiki/Comet.

David Morrison
Director, NASA Lunar Science Institute

October 1, 2009

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