by Jim Nintzel
One of The Range's favorite spacecrafts is the Mars Reconnaissance Orbiter, which carries the UA's HiRISE camera high above the surface of Mars. One of HiRISE's latest photos of an impact crater is getting a lot of attention this month. Here's Bad Astronomy's Phil Plait at Slate:
Bang! That is one of the newest craters on Mars: It’s about 30 meters (100 feet) across, and formed by the explosive impact of an asteroid no more than four years ago. We know that because it wasn’t there in an image of Mars taken by the Mars Reconnaissance Orbiter spacecraft in July 2010, but it was in one taken in May 2012.
Plait goes on to explain how a recent experiment here in the Arizona desert gives us some idea of how big the meteorite was:
How big was the rock that did this, and how big was the resulting kaboom? Well, I can guess. In my TV show Bad Universe we detonated 7,500 pounds of ANFO (ammonium nitrate fuel oil mix)—the explosive equivalent of 1.5 tons of TNT—in the Arizona desert to simulate an asteroid impact. The crater we blasted out of the sand was about 20 meters across. The relationship between the size of an explosion and the size of the crater it leaves behind is complicated, but it’s safe to say that the explosive impact on Mars to form this new crater was at least twice as large as the one we set off, or three tons of TNT.