By United Press International Scientists in California and Italy say they have new evidence showing the mass extinction event that wiped out the dinosaurs was relatively brief, lasting about 10,000 years. Sujoy Mukhopadhyay, a graduate student at the California Institute of Technology, Pasadena, and his colleagues chemically dated the sedimentary rock layer whose distinctive characteristics mark the boundary between two periods in time. But until now, scientists had not been able to determine how long it took for that thin layer of clay to be deposited, meaning they have lacked knowledge of how long the extinction event lasted. They concluded the conditions that killed the dinosaurs were over in the blink of an eye, in geologic time. More specifically, they believe the object impacting the earth was not part of a comet shower, which would have left behind much more helium-3.
Comets are dusty objects.
They bring a lot of dust with them, and the dust attracts helium-3. Geochronology is the science of dating minerals. Mukhopadhyay believes his findings also provide some of the best evidence yet that the extinction of the dinosaurs was not caused, as some theories hold, by massive volcanic eruptions. He says an extinction event caused by volcanic eruptions would have likely lasted up to 500,000 years. Mukhopadhyay concedes the global environmental effects from extensive volcanic eruption could be similar to the effects from the impact of a single asteroid, but argues the time scale of the two processes would differ.