Big crater seen beneath ice sheet

Combined gravity and radar data reveal a crater formation deep under the ice (Image: OSU)

What appears to be a 480km-wide (300 miles) crater has been detected under the East Antarctic Ice Sheet.

The scientists behind the discovery say it could have been made by a massive meteorite strike 250 million years ago.

The feature at Wilkes Land was found by Nasa satellites that are mapping subtle differences in the Earth's gravity.

"This Wilkes Land impact is much bigger than the impact that killed the dinosaurs," said Prof Ralph von Frese, from Ohio State University, in the US.

If the crater really was formed at the time von Frese and colleagues believe, it will raise interest as a possible cause of the "great dying" - the biggest of all the Earth's mass extinctions when 95% of all marine life and 70% of all land species disappeared.

Some scientists have long suspected that the extinction at the boundary of the Permian and Triassic (PT) Periods could have occurred quite abruptly - the result of environmental changes brought on by the impact of a giant space rock.

(Thanks to Richard A Lupoff for directing me to this story. I think that he -- like most science fiction writers -- finds a bit of unreality in the way headlines increasingly seem to be stories written by him or others in the field many years ago.)

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