Summary
New studies using a Catastrophe Calculator show that the meteor responsible for creating Meteor Crater in Arizona hit Earth at a much slower pace. Initial calculations indicated that it hit Earth at a speed of no less than 34,000 mph (15 km/sec. The new analysis reveals it’s probably 26,000 mph (12 km/sec). This new data explains why there was less melted rock found in and around the crater.
Original source:
http://www.space.com/scienceastronomy/050309_meteor_crater.html
Details
The space rock that carved Meteor Crater in Arizona hit the planet much more slowly than astronomers once figured, but still 10 times faster than a rifle bullet.
The new analysis, announced today, explains why there's a lot less melted rock in the crater than expected.
The big hole in the ground -- 570 feet deep and 4,100 feet (1.25 kilometers) across -- was blown into existence 50,000 years ago by an asteroid roughly 130 feet (40 meters) wide.
Previous calculations had the rock slamming into the ground at no less than 34,000 mph (15 km/sec), based in part on the expected speeds of large meteors in relation to Earth.
A new computer model, reported in the March 10 issue of the journal Nature, shows the incoming object would have slowed considerably during its plunge through the atmosphere, part of it breaking into a pancake-shaped cloud of iron fragments prior to impact.
About half the original 300,000-ton bulk remained intact, smacking the planet at about 26,800 mph (12 km/sec), said the study's lead researcher, Jay Melosh of the University of Arizona.
Barringer and others found chunks of the iron space rock weighing from a pound up to 1,000 pounds in a 6-mile-diameter circle around the crater.
In 1908, a good-sized asteroid -- more stony in nature -- exploded above the surface of Siberia, flatting hundreds of miles of forest but leaving almost no extraterrestrial trace.
During the satellite era, scientists have monitored car-sized space rocks routinely exploding in the air.
The effect of screaming through the air, even for an iron-heavy meteorite like the one that struck Arizona, is a lot like hitting a wall, Melosh said.
"The weakened pieces began to come apart and shower down from about 8.
5 miles (14 kilometers) high.
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Tuesday, March 22, 2005
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