“I get these kinds of requests all the time,” said Rowley, “so at first I didn’t think about it too much. But when they asked to me take a closer look at the data and I saw the alignment, I just said, ‘wow!’”
Three of the five craters, Rochechouart in France, and Manicouagan and Saint Martin in Canada, were at the same latitude–22.8 degrees–forming a nearly 5000-kilometer chain. The other two, Obolon’ in Ukraine and Red Wing in Minnesota, lay on identical declination paths with Rochechouart and Saint Martin, respectively. All of the craters are previously known and well-studied, but the paleoalignment has never before been shown.
One possible explanation for the alignments of the five craters is a fragmented comet that crashed to Earth in three major groups over a period of time as short as four hours, in two groups of two and one solitary chunk. It is possible that the comet or asteroid actually broke into more than five pieces, but most of the Earth at that latitude was ocean 214 million years ago, and evidence of any ocean-bottom craters has long been obliterated. The impacts may have occurred over a period of several days, depending on how widely the fragments were dispersed.
Rowley said that the chance that these craters are randomly aligned is near zero.
Manicouagan, the largest of the five craters, is more than 100 kilometers in diameter, comparable to the 170-kilometer Chixulub crater in the Yucatan–the impact that is believed to have caused the mass extinction at the end of the Cretaceous period 65 million years ago, killing the dinosaurs.
The Triassic extinction was equivalent in magnitude to the Cretacious/Tertiary (K/T) extinction: about 80% of the species then living on the planet became extinct.
There are 150 known impact craters worldwide; the group is now studying other
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Contact: Diana Steele
d-steele@uchicago.edu
773-702-8366
University of Chicago Medical Center
12-Mar-1998