One that size could possible destroy Mars and we'd be in a world of poop. Just imagine the pieces of Mars heading our way. Not a good thought. Tho extinction for us does come to mind.

Naaah, it'd need to be something like a thousand times bigger to destroy Mars. Something like the size of Venus or Mercury might do it, or it would at the very least create enough debris to dramatically increase the possibility of an impact event on Earth. Planets are very difficult to kill. Very difficult...unless you have a Death Star, or access to a Black Hole.

This makes for good reading:
http://qntm.org/destroy

Plenty of things can destroy life, or forms of life on a planet, or radically change the ecosystem, but those events are contained to the planet it occurs on unless it's some sort of space ship, or a pulsar.

What this will likely do is radically change the climate patterns of Mars, certainly it will be difficult to see the surface of Mars for a while after impact, it will also generate a rather large hole and strip the surface clean for a very large distance surrounding the impact point. It will also make Michael Bay feel very very very small and impotent. Likewise Roland Emmerich.

However, the most likely outcome is that it will make a very pretty passing light show for the Curiosity rover and sail right past Mars and back out into space.

I'll just leave this here (thanks to HunterICX who linked me this ages ago):

http://www.youtube.com/watch?v=rjECbQ1r-k0

Oh GREAT! Give Bubblehead something else to start a wackadoodle thread about!
:haha:

I hope they trun Hubble towards Mars at that time, think of the pics it could get!

Not sure if i will be able to see anything or not, but I'm going to try. Got a twelve inch scope, just hope Mars will be visible to me that day. :hmmm:

I think half the telescopes in the solar system will be pointing at mars on that day if there is better than a 1/10 chance of an impact

Assuming they are not directly in the firing line MRO, Express, Oddysy, Curiosity and Opportunity should have some epic views of the blast and after effects

No doubt about that :yep:

If an object of similar size ever hits earth, it won't do too much damage. After all, most intelligent life here has already been and gone...

Well, to be fair, has it ever existed in Stoke? :O:

Oberon, what if by chance it knocks Mars out of it's orbit? 310 mlles across is one hell of a big piece of rock. And Mars isn't as large as Earth. :03:

I don't know if the mass of that comet is known, but if I'm not mistaken accelerating Mars enough to achieve Solar escape velocity or decelerating it to the point it will de-orbit into the sun will require orders of magnitude more kinetic energy than 20 petatons.

AFAIK the size of the comet hasn't actually been determined yet, so I'm not sure where you got 310 miles from, unless you mean the crater, which is not the same size as the impactor. A comet 310 miles wide coming in with the same speed of the comet in question would make a crater that is (quick calculations on impact website) a thousand miles across, but would probably still not do anything to Mars other than perhaps change the rotation speed by an infinitesimal amount, so a Martian day might go from being 24 hours 37 minutes to 24 hours 41 minutes. The tilt of the planet might alter a bit too, it's not particularly hard to alter axial tilts of planets, Earths has moved a couple of times recently, usually because of major earthquakes, the effects of such small shifts are usually pretty minor, if there are any at all.

No, this comet will create a large hole, a big fireball, a large shockwave and a massive debris cloud which will make things a bit dark underneath it for a while, but Mars itself will keep on spinning, just as Earth has kept on spinning despite being hit by objects potentially bigger than that comet.

Another thing to remember, that although the chances of an impact event on Mars are at 1 in 1250 (using the Monte-Carlo method), the current path of the comet puts it passing Mars further away than the recent Asteroid that shot underneath our comms satellites. :03:

So, it's one to watch, but it's 50/50 whether it'll actually impact or not, and if it does miss then there's still a chance of an impact further down the line depending on the orbital cycle of the comet. It could be a sight for our childrens childrens childrens....providing a more nearby comet or asteroid hasn't landed on US by then. :O: