Scientists in 2002 were convinced they had found
evidence that a gigantic meteorite, twice as big as the one which
is believed to have wiped out the dinosaurs, collided with Earth
billions of years ago.
A report published in the Science journal claimed
that deposits of the rock were found in South Africa and Australia.
The asteroid, twenty kilometres wide (twelve miles), is believed to
have hit the planet with such force that it would have generated tidal
waves kilometres high, with the bottom of the ocean being torn up.
Researchers from Stanford University in California
and Louisiana State University stated that the cataclysmic event
happened about 3.4 billion years ago, before continents were formed
and when only bacteria existed. It is not known exactly where the
giant meteorite hit as the scientists had not yet located a crater
which would have been left by the impact.
The report said the rock probably came from the
asteroid belt between Mars and Jupiter. Researcher Gary Byerly said
the object was likely to have been part of a shower of meteorites,
some as wide as fifty kilometres (thirty miles).
The impacts were very large, changing the course of
evolution on Earth. The report did not say what changes the impact
may have affected. There isn't a big extinction event that can be
identified that is as cut-and-dried as the extinction of the dinosaurs,
according to report co-author, Donald Lowe.
'Incredible tidal waves'
Mr Lowe said it would have taken the rock less than
two seconds to pass through the ocean and slam into the sea bed. That
impact would generate enormous waves kilometres high that would spread
out from the impact site, sweeping across the ocean, and producing
incredible tidal waves - causing a tremendous amount of erosion on the
microcontinents and tearing up the bottom of the ocean.
Geologists found traces of the meteorite in South
Africa's Barberton greenstone belt and Pilbara block in western
Australia. The sites contain rocks which were formed more than three
billion years ago and which contain information dating back to the
beginning of the solar system.