Posted: Fri, Feb 23, 2001, 12:34 PM ET (1734 GMT)
Scientists now believe that not only did an asteroid impact 65 million years ago wipe out the dinosaurs, a similar large impact 250 million years ago may have set the stage for their reign on the planet to begin, according to work published in Friday's issue of the journal Science. A group led by Luann Becker of the University of Washington discovered a concentration of complex carbon molecules known as fullerenes or "buckyballs" in layers of rock dating back 250 million years, a time when 90 percent of the species on the planet suddenly died out. Analysis of the fullerenes show they have an extraterrestrial origin, likely from an asteroid or comet that collided with the Earth, triggering volcanic eruptions and other events that killed off most of the life on the planet, clearing the way for dinosaurs. The layer of fullerenes is similar to the layer of the heavy metallic element iridium found in rocks dating back to the demise of the dinosaurs: the reason why fullerenes were found in one case and iridium in another may be related to differences in the composition of the impacting body.

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