http://www.globeandmail.com/servlet/story/RTGAM.20031120.wmete1120/BNStory/International/ Meteor blamed for second mass extinction Associated Press Washington — A massive asteroid may have collided with the Earth 251 million years ago and killed 90 per cent of all life, an extinction even more severe than the meteorite impact that snuffed out the dinosaurs 66 million years ago. A new study, based on meteorite fragments found in Antarctica, suggests the Permian-Triassic event, the greatest extinction in the planet's history, may have been triggered by a mountain-sized space rock that smashed into a southern land mass. "It appears to us that the two largest mass extinctions in Earth history ... were both caused by catastrophic collisions" with meteoroids, the researchers say in their study appearing this week in the journal Science. Asish Basu, a professor of Earth sciences at the University of Rochester, said proof of a massive impact 251 million years ago is in the chemistry found in rocky fragments recovered on Graphite Peak in Antarctica. He said the fragments were found at a geological horizon, or layer, that was laid down at the start of the Permian-Triassic extinction. Analysis shows the fragments have chemical ratios that are unique to meteorites. "The only place you would find the chemical composition that we found in these fragments is in very primitive, 4.6-billion-year-old meteorites, as old as our Earth," said Dr. Basu, the first author of the study. Dr. Basu said the Permian-Triassic asteroid was probably bigger than the almost-10-kilometre-wide space rock that is thought to have killed the dinosaurs. Such an impact could cause a huge fireball and send billions of tonnes of dust into the atmosphere, enough to darken the sun for months. It also would have laid down a layer of dust bearing the same chemical composition as the meteorite. The dinosaur-killing asteroid left a thin layer of the element iridium across the globe. But Dr. Basu said iridium was not found in the fragments recovered from the Antarctica, suggesting the earlier Permian-Triassic asteroid had a different composition. Dr. Basu said specimens recovered from Permian-Triassic rock formations in China, however, have a chemistry that matches that of the meteorite fragments found in Antarctica, a discovery that supports the impact theory. Also, shocked quartz, a telltale sign of an asteroid impact, has been found at both sites, he said. At the time of the Permian-Triassic event, Africa, South America, India, Australia and Antarctica were joined in a giant continent called Pangea. Just where the asteroid hit in that land mass is uncertain, Dr. Basu said, but it could have been near what is now western Australia. Life on Earth 251 million years ago was far different from what it is now or what it was when dinosaurs lived. "There were no large animals then, but there were lots of species living on the land and in the sea, and there were plants," said Dr. Basu. The most dominant plant, which is found commonly in fossil beds from the Permian-Triassic, was a giant fern called glossopteris. In the geological layers following the impact, that fern is absent from the fossil record. "That was the last blooming of that plant," said Dr. Basu. "After that, it was gone forever from the planet." Massive outflows of lava, called flood basalt, occurred around the time of both the Permian-Triassic and the dinosaur extinctions. The outflow continued for thousands of years and thickly covered hundreds of kilometres. Dr. Basu said it is possible that asteroid impacts triggered both eruptions of lava, but the connection has yet to be proven. Some experts are skeptical that Dr. Basu and his co-authors have found 251-million-year-old meteorite metals, although nobody questions that the material did come from outer space. The surprise is that the specimens survived the weathering on Earth for so long. "Nobody has even seen anything like this before," said Jeffrey Grossman, a researcher with the United States Geologic Survey in Reston, Va. "It is incredibly fresh and that is astonishing." David Kring, a planetary geologist at the University of Arizona, said it is clear that material found by Dr. Basu and his team is from an asteroid, "but it is unlike the debris we have seen in other impact ejecta." As a result, said Sr. Kring, "there are enough questions ... that I don't think one can say that an impact is conclusively linked to the Permian-Triassic extinction. We need to go back and test the hypothesis."
This is really a significant announcement. The Permian extinction damned near brought all life to an end, and the "uh, big volcano!" theory was obviously pretty weak. I saw a talk this year on a guy who works on a NASA project of cataloguing all space rocks that could ever possibly approach Earth. So far, they've located about 80% of all near Earth-orbit rocks, and things look good so far, but there are always new rocks entering the inner solar system, so you can never really be totally safe. Here's an interesting graph on how frequently we can expect big impacts on Earth eek. The Y axis is weird. It's sort of inverse time -- basically just read it as "frequency," with more frequent being higher on the axis. When they first derived this graph from looking at moon cratering and the fossil record, they said "holy crap! we should be getting an impact equal to a thermo-nuclear device every freakin year! And... when they checked with some air force folks who do super-sensitive detection work, it was true. These events do happen, but the rocks completely explode in the upper atmosphere and most of us choads never notice. Cool cool topic. My nerd-o-meter is off the chart here.
Only 119 million years until the next mass extinction...Hopefully, everybody has plenty of canned goods and bottled water...
Funny, but statistics don't work that way, of course. A catastrophic event happens, on average, every 20,000 years. So, this could easily happen one hour from now. It probably won't, but you just don't know. I'm praying for a Salt Lake City impact.
I can already see it. April 10, 2004: Houston at Utah. With three minutes to go in the game, the Rockets are beating the Jazz by 25, simultaneously clinching their first Midwest Division title in 10 years and sending Utah to it's first ever lottery season. As Jeff Van Gundy takes his starters out of the game during a time out, the skies over Salt Lake City begin to darken..........
Well on your advice B-Bob I have completely sealed my house with hefty bags and duct tape in the event Comet Encke (about to make a close pass) decides to make our little planet its final resting place. FYI - Hefty bags and duct tape (not duck tape that attracts them) are a known and proven comet repellent. Whew! All this work has tired me out - I seem to be a little out of breath - um is it normal to turn blue after.......................................................................
As long as they're playing the Lakers and not the Rockets when it happens. I'll say it again... more money and brains for NASA!!!
Why? Four years without playoffs. Waiting for Eddie Griffin to grow up. Watching Moochie dribble. These are a few of my favorite things.
I love playing the stiff scientific straight man (if you know what I mean) for all the comics here. Nice work guys!
I've actually met this guy, he's pretty cool and definitely knows what he's talking about. I work for one of his colleagues.
That's not an abstract enough noun, ZRB. Maybe he could launch the "War on Mysterious Threats from Outer Space" or something like that.
