Prague, 18 May 2004 (RFE/RL) -- Scientists from the University of California say they have found evidence that a huge meteor struck the Earth near what is now the northwest coast of Australia. And they believe the impact could be associated with the almost total destruction of life on Earth 250 million years ago.
It is widely believed that a combination of a giant meteor landing in what is now Mexico, combined with a massive volcanic eruption, wiped out many life forms -- including the dinosaurs -- some 65 million years ago.
However, it was also known that a far more devastating catastrophe wiped out many more life forms 250 million years ago. But its cause has long been debated by scientists.
Now, after five years of research and exploration, a team of U.S. scientists believe they have proof that the earlier disaster was also caused by a similar conjunction of events.
The leader of the team of scientists is Dr. Luann Becker of the geophysics department at the University of California at Santa Barbara. She said the impact from the meteor -- with an estimated 200-kilometer radius -- and the airborne ash from the volcanic eruptions could have blocked sunlight from reaching the Earth for years and might be responsible for what is called the "Great Dying" during the period geologists refer to as the End-Permian.
“Ninety percent of all the marine organisms, [and] 70 to 80 percent of all the land animals and plants were wiped out in a very, very fast, quick, abrupt way.” -- Dr. Luann Becker of UC Santa Barbara
“Accompanying this time period 250 million years ago is the greatest mass extinction in the history of life on our planet,” Becker said. “Ninety percent of all the marine organisms, [and] 70 to 80 percent of all the land animals and plants were wiped out in a very, very fast, quick, abrupt way,” Becker says.
Within the last five years, Becker's team found tiny fragments of quartz in rocks in Antarctica that had been marked by what looked like the shock of an extraterrestrial impact. They also identified molecules of extraterrestrial gases in 250 million-year-old rocks from China.
The scientists also say that blobs of metal found in the rock might have been formed by an extraterrestrial impact and that small glassy drops in the rocks could also have been produced during the searing heat of impact.
Becker says that although the evidence they had gathered pointed to a meteorite impact, they did not know where it had struck.
"The obvious thing that people were asking us was, 'Well, where in the world would you look for an impact crater and, if so, can you find it?'" Becker says.
She says the scientists drew a map of what the world looked like 250 million years ago, when there was just one huge land mass called Pangea. They charted the places in China, Antarctica, and Australia where the various bits of evidence had been found.
"We were able to assemble the data, and we saw a very obvious trend that most of the impact debris at that time was in the Southern Hemisphere and, in particular, between Australia, Africa, and what was then India. It was all then joined together in the extreme Southern Hemisphere," Becker says.
Becker says the search area eventually was narrowed down but still consisted of a vast area.
"So we began to wonder whether we could find an impact crater. And that is when we sort of stumbled onto the Bedout High offshore northwestern Australia," Becker says.
The scientists discovered that oil companies in the 1970s and 1980s had drilled two core samples deep below the ocean's surface at a place called Bedout High.
They were astonished to find that the samples had never been analyzed and were still preserved at an Australian college. Becker says the analysis convinced them that Bedout High was the site of the meteor impact 250 million years ago.
"What we have interpreted in the cores is what we believe is part of the melt sheet, the material on the very lower part of the crater floor, which has seen the highest amount of temperature, the highest amount of pressure, and this is the material that we are looking at. What it has in it is a lot of shocked (compacted by massive force) minerals, but this stuff has been completely converted to glass, and there is no known geological process on the Earth that can do that. It simply can't be done, even in the most explosive volcanic event," Becker says.
Becker says the samples are similar to those found at the site of the Mexican meteor impact 65 million years ago.
Many scientists reject Becker's suggestion that volcanic activity was triggered or increased by the meteor impact, and some contest her theory that a meteor was involved at all in the "Great Dying."
Impact expert David Kring from the University of Arizona says that all the evidence can be explained without invoking an extraterrestrial impact. For instance, the meteorite fragments could have been a sprinkle of small meteorites like those that regularly bombard the planet.
Other skeptics ask how the meteorite fragments were preserved so well over 250 million years.
Becker and her team have counterarguments, but agree that more research needs to be done.
"The next thing we'd like to do is, we would love to have an opportunity to explore this crater more from the geophysical perspective. We would certainly like to have an opportunity to define how big the crater is. We simply don't have the data to do that," Becker says.
She says they are approaching energy companies for funding because the research could help in identifying sites rich in oil and natural gas.