[meteorite-list] Antarctic Craters Reveal Strike

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Aug 19 13:08:53 2004
Message-ID: <200408191708.KAA22999_at_zagami.jpl.nasa.gov>

http://news.bbc.co.uk/1/hi/sci/tech/3580230.stm

Antarctic craters reveal strike
BBC News
August 19, 2004

Scientists have mapped enormous impact craters hidden under the
Antarctic ice sheet using satellite technology.

The craters may have either come from an asteroid between 5 and 11km
across that broke up in the atmosphere, a swarm of comets or comet
fragments.

The space impacts created multiple craters over an area of 2,092km (1300
miles) by 3,862km (2,400 miles).

The scientists told a conference this week that the impacts occurred
roughly 780,000 years ago during an ice age.

When the impacts hit, they would have melted through the ice and through
the crust below.

Professor Frans van der Hoeven, from Delft University in the
Netherlands, told the International Geographical Union Congress in
Glasgow that the biggest single strike seared a hole in the ice sheet
roughly 322km (200 miles) by 322km.

Impact melt

This would have melted about 1% of the ice sheet, raising water levels
worldwide by 60cm (2ft).

The research suggests that an asteroid the size of the one blamed for
killing off the dinosaurs 65 million years ago could have struck Earth
relatively recently.

Early humans would have been living in Africa and other parts of the Old
World at the time of the strikes.

But the impacts would have occurred during an ice age, so even tidal
waves would have been weakened by the stabilising effect of icebergs on
the ocean.

The craters were resolved using satellite data to map gravity anomalies
under the ice sheet.
Received on Thu 19 Aug 2004 01:08:26 PM PDT