Post by Chicago Astronomer - Astro Joe on Jun 3, 2006 6:29:40 GMT -6
Antarctic crater wiped out life
Space scientists have discovered a crater the size of England from an asteroid impact that wiped out nearly all life.
The hole was blasted out of the Earth by a cosmic missile 250 million years ago. It was spotted, half a mile under the ice in the Antarctic, by Nasa satellites.
Experts say the killer asteroid was around 30 miles wide, five times the diameter of another that hit the Earth 65 million years ago, dooming the dinosaurs. The older crater lies in the Wilkes Land area of eastern Antarctica. Researchers believe the impact was so powerful that it triggered the break-up of a supercontinent called Gondwana, pushing Australia northwards. The catastrophic consequences also caused the greatest mass-extinction ever on Earth, wiping out virtually all life on land and in the sea.
The crater's location was discovered by twin Nasa satellites called Grace which work together to map the gravitational pull of the Earth. They found a mass concentration of material at Wilkes Land typical of that produced by a meteor impact. Follow-up studies using aircraft radar detected a circular ridge 300 miles wide under the ice, the rim of the impact crater.
Geology professor Ralph von Frese, of Ohio State University, who led the discovery team, said: "This impact is much bigger than the one that killed the dinosaurs and probably would have caused catastrophic damage."
Dinosaurs which later took over the world were wiped out after an asteroid six miles wide hit the Yucatan peninsula in Mexico.
Source: skymania.blogspot.com/2006/06/antarctic-crater-wiped-out-life.html
And another good source is here at Nature.com: www.nature.com/news/2006/060529/full/060529-11.html
===========
Antarctica was once lush and tropical. I wonder if this was the end of that, and what is under all that snow and ice?..
