Friday, November 21, 2003
Meteor Killer
It has been sort-of accepted in scientific circles that it was a meteor strike 65 million years ago that wiped out the dinosaurs, among others. Kenneth Chang writes about a paper published in Science today that suggests that there was a much larger meteor strike 250 million years ago that led to the extinction of nearly 90% of the species alive then. Perhaps it's time to pay more attention to NEAT?
The researchers report that they found the meteorite fragments in rocks in Antarctica that date from the Permian-Triassic boundary. The mineral composition of the fragments, each less than one-fiftieth of an inch wide, correspond to that of certain meteorites and is like nothing found naturally on Earth, they reported. In addition, the scientists said, the same rocks had previously yielded soccer-ball-shaped molecules known as buckyballs containing extraterrestrial gases, as well as grains of quartz with fractures that indicate a tremendous shock.
Skeptics abound.
Dr. Eldridge Moores, an emeritus professor of geology at the University of California at Davis, described the meteorite fragments as "the most interesting evidence for a meteorite event at this boundary that I've seen so far." But, he added, while the evidence for the dinosaur-killing meteor 65 million years ago is a convincing 10 on a 1-to-10 scale, the evidence for a killer meteor at the Permian-Triassic boundary is not nearly as solid.
Dr. Frank Kyte of U.C.L.A., who several years ago discovered a fragment of the meteor that killed the dinosaurs, said the fragments described in the Science paper do possess the chemical signatures that they came from outer space, "but it's a little unbelievable they've survived for a couple hundred million years in the sediment." The shards, Dr. Kyte said, could be merely interplanetary dust that floated down through the atmosphere.
The researchers report that they found the meteorite fragments in rocks in Antarctica that date from the Permian-Triassic boundary. The mineral composition of the fragments, each less than one-fiftieth of an inch wide, correspond to that of certain meteorites and is like nothing found naturally on Earth, they reported. In addition, the scientists said, the same rocks had previously yielded soccer-ball-shaped molecules known as buckyballs containing extraterrestrial gases, as well as grains of quartz with fractures that indicate a tremendous shock.
Skeptics abound.
Dr. Eldridge Moores, an emeritus professor of geology at the University of California at Davis, described the meteorite fragments as "the most interesting evidence for a meteorite event at this boundary that I've seen so far." But, he added, while the evidence for the dinosaur-killing meteor 65 million years ago is a convincing 10 on a 1-to-10 scale, the evidence for a killer meteor at the Permian-Triassic boundary is not nearly as solid.
Dr. Frank Kyte of U.C.L.A., who several years ago discovered a fragment of the meteor that killed the dinosaurs, said the fragments described in the Science paper do possess the chemical signatures that they came from outer space, "but it's a little unbelievable they've survived for a couple hundred million years in the sediment." The shards, Dr. Kyte said, could be merely interplanetary dust that floated down through the atmosphere.
