March 10, 2005Call it the mystery of the nonmelting meteorite: For decades scientists have wondered how a meteorite powerful enough to have made Arizona's Barringer Meteor Crater (pictured) could have left hardly any melted rock in its wake. Now a report in this week's issue of Nature looks to have closed the case.
Prevailing wisdom had the meteorite speeding at 45,000 miles (72,000 kilometers) an hour when it hit. But H. Jay Melosh, of the University of Arizona, and Gareth Collins, of Imperial College London, used mathematical models to show that the space rock was likely hurtling at a mere 25,000 miles (43,000 kilometers) an hour.
Why the slowdown? "The meteorite had probably been cracked from collisions in space," Melosh said in a statement. When the rock slammed into Earth's atmosphere some 50,000 years ago, half of it likely went to pieces. "As they came apart, atmospheric drag slowed them down, increasing the forces that crushed them so that they slowed and crumbled more."
Now falling relatively gently, the approximately 65-foot-wide (20-meter-wide) chunk that remained intact crashed into the desert floor. It would have hit with the force of 150 Hiroshima bombs, creatingbut not meltingthe 0.75-mile-wide (1.2-kilometer-wide) pit we know today.
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