Evidence from 65-million-year-old sediments suggests that a single impact from space wiped out the dinosaurs and that ecosystems recovered from the trauma in only a few thousand years.
Researchers analyzed layers of ocean sediments deposited during a 1.5-million-year period in Italy and Tunisia. Among these was the thin clay layer that marks when the dinosaurs became extinct. The scientists found that the concentrations of the isotope helium-3 in the sediments didn't vary during those 1.5 million years. This indicates that the extinction-triggering object that struck Earth 65 million years ago wasn't part of a long-term comet shower, the researchers say.
Such a shower would have produced far more comet dust and delivered far more helium-3, which is 300 times more common in space than on Earth, says Sujoy Mukhopadhyay, a geochemist at the California Institute of Technology in Pasadena.