Astronomers are completely confident that the 150-foot-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. But then
again, a meteorite just exploded in Russia. So what would really
happen if their calculations are wrong? To answer this, first we
should find out how much energy 2012 DA14 could release if it
crashed into 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 Natural
History—three other scientists asked themselves this question in
2010: Robert Marcus, H. Jay Melosh, and Gareth Collins. More
reading: We Are Safe! The Asteroid Is Leaving Now • Video of
2012 DA14 as it approaches Earth at five miles per second •
Meteorite explodes over Russia, panic spreads Ebel says that
Marcus et al calculated the kinetic energy of a 50-meter-wide
asteroid with a density