<story><title>Comet might hit Mars in 2014</title><url>http://science.nbcnews.com/_news/2013/02/26/17107085-comet-just-might-hit-mars-in-2014</url><text></text></story><parent_chain></parent_chain><comment><author>btilly</author><text>Wow.  What are the odds?&lt;p&gt;Just doing quick ratios and squaring them, if the comet follows the initial projections, there are only about 230 large objects coming this close for every one that actually lands on Mars.  (And Earth gets hit with about 3.5 of these for every one that hits Mars.  Our last is estimated to be 65,957,000 +- 11,000 years  ago.)  This is literally a once in a million years near miss!&lt;p&gt;Of course the odds now are much higher than they normally would be.  The fact that it is on a hyperbolic orbit means that it comes from outside of the Solar System.  The density of such objects is much higher near the galactic plane than elsewhere.  However the Sun bobs up and down, spending most of its time away from the galactic plane and crossing it every 30 million years or so.  We last crossed it something like 100,000 years ago and are now heading away, so are still in a period where interstellar objects are more likely to come barreling through.  So the odds are higher than they normally are, but even if you generously account for the currently increased risk, this is still a once in a civilization near miss.&lt;p&gt;Of course the initial estimate may be wrong.  From the article the uncertainty is much bigger than the distance to Mars.  If the uncertainty is the stated 650,000 miles, then we&apos;ve got roughly a 1/24,000 chance of a direct impact.  (I am sure that more informed people will come up with much better estimates in the not too distant future.)</text></comment>
<story><title>Comet might hit Mars in 2014</title><url>http://science.nbcnews.com/_news/2013/02/26/17107085-comet-just-might-hit-mars-in-2014</url><text></text></story><parent_chain></parent_chain><comment><author>alexandros</author><text>Witnessing such an event could help get humanity serious about existential risk, from comets or otherwise. I, for one, am hoping for an impact.</text></comment>