06-30-2006 - Earth

sagar: Author=’Jorge Salazar’ program=’4926′ video=”Artist’s rendition of a colossal meteorite that scientists at Ohio State University think struck the Earth over 250 million years ago. Using gravity measurements from NASA’s GRACE satellites along with aerial radar, scientists have detected signs of what might be a 300 mile wide impact crater buried under a mile of Anatarctic ice. More images below._JB:_ I’m Joel Block.

_DB:_ And I’m Deborah Byrd for “Earth & Sky”:/http://208.96.63.114/. Scientists have found the first evidence of what they think is an enormous impact crater in Antarctica.

_JB:_ The research team was led by geophysicist “Ralph von Frese”:http://www.geology.ohio-state.edu/modules.php?op=modload&name=Faculty&id=vonfrese@geology.ohio-state.edu&file=faculty.profile of Ohio State University. Von Frese examined data from a satellite that mapped subtle differences in Earth’s gravitational field. He found a large area in Antarctica of unusually dense rock. Radar images from aircraft revealed a large basin, which von Frese thinks is an impact crater 500 kilometers, or about 300 miles wide.

_Ralph von Frese:_ For impact craters, there’s a sort of Mexican hat, or sombrero anomaly in the gravity field that is quite recognizable when you see it. And it’s complimented by a crater.

_DB:_ A meteorite strike this large would have wreaked havoc for life on Earth. Von Frese thinks it might be associated with the “Permian-Triassic extinction”:http://en.wikipedia.org/wiki/Permian-Triassic_extinction, which is thought to have extinguished 95% of all life on Earth, about 250 million years ago.

_Ralph von Frese:_ People have started looking at meteorite impacts as a possible agent for these extinctions.

_JB:_ But scientists haven’t yet collected an actual piece of the giant meteorite, which would be buried beneath more than a kilometer of ice. More at earthsky.org. Thanks today to “NASA”:http://www.nasa.gov. We’re Block and Byrd for “Earth & Sky”:/http://208.96.63.114/.

Written by EarthSky