[meteorite-list] 145-Million-Year-Old Morokweng Impact Crater

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Aug 3 12:11:14 2006
Message-ID: <200608031520.IAA11860_at_zagami.jpl.nasa.gov>

http://www.vuvuzelaonline.com/index.php?option=com_content&task=view&id=483&Itemid=51

Our Boffins find 145-million-year-old meteor relic
Written by MARIZANNE KOK
Vuvuzela Online
03 August 2006

THREE Wits academics were part of an international team that found
pieces of an ancient asteroid in the Morokweng crater, located beneath
the sands of the Kalahari Desert.

Dr Marco Andreoli, Prof Lew Ashwal and Prof Rodger Hart, all involved
with the Wits School of Geosciences, were among the team of 11 who
drilled loose an asteroid relic and subsequently published an article
about the find in the Nature journal.

A soccer-ball-sized meteorite fossil was discovered in the Morokweng
crater when scientists drilled holes into the area where an asteroid
with a diameter of 5-10km struck the Earth 145 million years ago.
 
It is a groundbreaking discovery because scientists commonly accepted
that objects melted or vaporised at the moment they crashed into the
Earth's surface.

The collision of an asteroid with the rocky surface of our planets
generates enormous heat which has the potential to turn rocks into gas
It is reported that a 10km-diameter object will produce temperatures of
between 1 700 and 14 000?C.

The Morokweng crater is now 70km wide, but according to Prof Ashwal it
was probably much bigger after the initial impact. It possibly became
smaller because of the effects of erosion over time.

The discovery of a 25cm-long asteroid relic, the first ever to be found
on Earth, will not only enable scientists to study a piece of space rock
that hit the earth millions of years ago, but it can also help them to
understand the different kinds of meteorites in existence. It blows the
field of meteorite study wide open.

"We now need to rethink everything we ever thought we knew about
meteorite craters," said Ashwal.

According to Ashwal, the team went to the Morokweng crater to "look for
something". "We're geologists, we go wherever we think there's a chance of
finding something. We had no idea we would find something like this," he
told Vuvuzela.

Ashwal said that a colleague assembled a group who could drill in the
Morokweng crater many years ago. The crater cannot be seen from the air
because it is covered with sand.

The only way it could be found was through geophysical photography,
which takes a picture of an area's magnetic field.

On such photographs it is easy to spot circles on the planet's surface,
which can only be one of a few things. These include volcanoes or, as
in the case of Morokweng, meteorite craters.

Ashwal said he and the rest of the team had been very surprised by the
public's reaction to the discovery. The professor himself has already
appeared on television and has done numerous interviews with radio
stations, magazines and newspapers.

"People's imaginations have really been captured by this. Of course
Hollywood movies like Armageddon have played a part in the public's
interest in these things, but we're not complaining."
Received on Thu 03 Aug 2006 11:20:35 AM PDT