From: http://www.gizmodo.co.uk/2013/02/what-would-actually-happen-if-the-2012-da14-asteroid-hit-earth-today/
By Jesus Diaz--"Astronomers are completely confident that the 45-metre-wide asteroid 2012 DA14 is not going to hit us, passing “only” at 17,200 miles from Earth — the closest encounter with an asteroid ever predicted. It’s a close call, but we will be safe. Given what’s happened in Russia today — what would really happen if their calculations were wrong?
To answer this, first we should find out how much energy could 2012 DA14 release if it crashed against our planet. According to Denton Ebel — Chair of the Division of Physical Sciences and Curator of the Department of Earth and Planetary Sciences at the American Museum of National History — three other scientists asked themselves this question in 2010: Robert Marcus, H. Jay Melosh, and Gareth Collins.
Ebel says that Marcus et al calculated the kinetic energy of a 50-metre-wide asteroid with a density of 2.6 grams per cubic centimetre and a speed of 12.7 kilometres per second hitting Earth at a 45 degree angle. This would be a very similar scenario to 2012 DA14, which is only five metres smaller and, in the opinion of Ebel, “could have a density of about 2.6 grams per cubic centimetre” since it is a stony asteroid. He says that the density may be less, since “most asteroids are underdense (lots of void space)” but let’s assume it’s 2.6 grams/cc for the sake of this argument.
Marcus, Melosh and Collins’ calculations resulted in 3.3 Megatons of kinetic energy at entry, with an airburst energy of 2.9 Megatons at about 8.5 km from the surface, “about the cruise altitude of passenger jets.” This means that an asteroid like this would likely explode in the air, releasing the energy equivalent of about 138 atomic bombs like the one that the Boeing B-29 Superfortress Enola Gay dropped over Hiroshima on August 9, 1945. Or, if you would like a more modern equivalent, 2012 DA14 could explode with the energy of nine W87 nuclear warheads like the ones carried by the American Minuteman III Iintercontinental ballistic missiles."
Read the rest here: http://www.gizmodo.co.uk/2013/02/what-would-actually-happen-if-the-2012-da14-asteroid-hit-earth-today/
