Wow. What are the odds?<p>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!<p>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.<p>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'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.)
50km is massive.<p>Earth's largest crater[1] is 300km across, and that's thought to have been created by an asteroid 5-10km in diameter. The 180km Chicxulub crater[2] (this impact is generally believed to be largely responsible for the extinction of dinosaurs) was around 10km in diameter.<p>I'm kind of hoping this turns out to be something. I thought the Russian meteor the other week was a most amazing natural event, and something far bigger than that would be incredible (not to mention safe for humanity in this case).<p>EDIT: 50km is actually the upper estimated limit of the size of this comet. Wikipedia[3] says 8-50km. It's still huge.<p>1: <a href="http://en.wikipedia.org/wiki/Vredefort_crater" rel="nofollow">http://en.wikipedia.org/wiki/Vredefort_crater</a>
2: <a href="http://en.wikipedia.org/wiki/Chicxulub_Crater" rel="nofollow">http://en.wikipedia.org/wiki/Chicxulub_Crater</a>
3: <a href="http://en.wikipedia.org/wiki/C/2013_A1" rel="nofollow">http://en.wikipedia.org/wiki/C/2013_A1</a>
I got to thinking. Is there any chance we could nudge this to impact the Hellas Planitia on Mars. It's the lowest point of Mars and therefore already has a higher atmospheric density (.01 ATM). So if we could double the depth and potentially add more water, it would really get us closer to a great location for a colony.<p><a href="http://en.wikipedia.org/wiki/Hellas_Planitia" rel="nofollow">http://en.wikipedia.org/wiki/Hellas_Planitia</a>
This is hyperbole. (no pun)<p><i>"Comet C/2013 A1 may fly past at a very safe distance of 0.008 AU (650,000 miles)," O'Neill wrote, "but to the other extreme, its orbital pass could put Mars directly in its path.</i>
There is a more recent post from Leonid Elenin with updated data:
<a href="http://spaceobs.org/en/tag/c2013-a1-siding-spring/" rel="nofollow">http://spaceobs.org/en/tag/c2013-a1-siding-spring/</a><p>"the comet might pass just 41,000 km [...] from the planet’s centre [...] 100% certainty that the planet will pass through the gaseous envelope of the comet [...] will be subject to intensive bombardments by microparticles which, among other things, might cause malfunction of the space probes currently there."
Wouldn't this be helping us terraform Mars faster? I think a lot of CO2 is trapped in ice on Mars, and we'd need that to make (presumably genetically enhanced) plants live there. A body that large hitting Mars could help raise its temperature.
If it does infact hit, will there be enough time b/w impact and shock wave for curiosity to upload a high def video of the asteroid entreating the atmosphere to a satellite if it is in it's vicinity?
Can anyone calculate how much this impact might heat up Mars? (I've heard even a little heating might set off a chain reaction and substantially increase the temperature?)
A direct hit doesn't seem to be all that probable, but Mars is still likely to pass within the comet's coma and be pelted by debris [1].<p>[1] <a href="http://www.slate.com/blogs/bad_astronomy/2013/02/28/mars_impact_the_red_planet_may_get_hit_by_a_comet_in_october_2014.html" rel="nofollow">http://www.slate.com/blogs/bad_astronomy/2013/02/28/mars_imp...</a>
I would think that an impact of mars by this body would delay any further plans of visiting mars for a while. The level of atmospheric dust would be... tremendous. I wonder if 'backsplash' of rocks and other material would pose a threat to the mars orbiters?
Hm. Interesting to observe, but will this throw a lot more crap into space that we then have to worry about in a few decades?<p>I assume it'll knacker any landers we have there as well through either seismic activity or dust penetration.
Watch this recent episode of Colbert, and his interview with Michio Kaku, where they talk about the recent asteroids, and also about the much larger one "grazing" Earth's atmosphere in 2029, and that "may" hit Earth in 2036 (depending on how much it grazes Earth's atmosphere in 2029). It starts at 15:30 or so:<p><a href="http://www.colbertnation.com/full-episodes/tue-february-26-2013-dr--michio-kaku" rel="nofollow">http://www.colbertnation.com/full-episodes/tue-february-26-2...</a>