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Old 05-03-2013, 07:14 PM
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renormalised (Carl)
No More Infinities

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Join Date: Apr 2008
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I think all too many of you are getting carried away with "doom and gloom" hysteria here. Let's just get a little bit of perspective here.

Yes, if this comet does look like it will impact Mars, it doesn't matter what it is made out of, it will impact. Even if it comes in at a shallow angle, i.e. travels through a lot of atmosphere before it impacts. Mars' atmosphere is too thin to prevent bodies of a significant size from impacting (anything larger than about 1 metre in size, and of the right composition). It will also most likely be a significant impact, just given the kinetic energy derived from its orbital velocity. However, the final explosion equivalent will be predicated on just how large the comet's nucleus actually is. That's yet to be really determined. If it is 50km in size, the amount of energy imparted on impact will be a simple matter of its kinetic energy on impact...which will be large. As to its size compared to Chicxulub, that depends on its composition. Typical comets have a density of around 1.2-2.5 grams per cubic centimetre. That directly effects its mass and therefore the kinetic energy of the impact. The Chicxulub impactor was a stony-iron asteroid, which have densities around 3.2-5 grams per cubic centimetre (depending on iron content).

Now, for the ejecta from the impact...whether any of it heads towards our planet and collides with it will depend on so many extraneous factors that the only thing that can be said about this is that it is possible, but not probable. It depends on where the comet hits on the planet, the impact energy and how much debris is lofted out of the Martian gravity well. As for large pieces being blasted out that could cause significant damage to Earth, that is taking things a little too far. Any pieces which did come towards our planet would be on the order of the Chelyabinsk Meteorite at their largest, however it's the numbers of pieces which would be of concern. As for splitting Mars apart...there's no worries that this will happen. It would take many orders of magnitude a strike on a planet the size of Mars, than this object could deliver, to blast the planet into debris. There's no need for any apocalyptic nonsense to be spread around in this forum or any other.
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