New evidence says Earths greatest extinction caused by ancient...( Long before the dinosaurs ever lived t...)

"An ancient meteorite body, one from the days when the solar system was still forming, struck the Earth 251 million years ago," says Asish Basu, professor of earth sciences in today's issue of Science. The research is the latest volley in a decades-long debate over what caused "The Great Dying," the greatest elimination of life in the planet's history.

While scientists have been wrangling over whether a meteor caused this great extinction ever since a meteor was fingered with the blame for the later dinosaur extinction, these new findings add weight to the argument that a major meteorite did strike the Earth 251 million years ago, likely triggering climate change and unprecedented volcanic activity. That one-two punch so affected the composition of the atmosphere that it took thousands of years to recover--leaving only a relative handful of plants and animals alive.

Two decades ago, Nobel laureate Luis Alvarez and his son, Walter, detected huge concentrations of iridium throughout the world in rock dated to the end of the dinosaur era. Iridium is only found in such concentrations in asteroids, so they concluded that a giant asteroid had struck the Earth at that time, likely leading to the downfall of the dinosaurs. The Alvarez claims were at first largely dismissed, but the evidence grew and today it is accepted that their interpretation was largely correct.

Basu added weight to the Alvarez claims in 1988 when he announced the discovery of "shocked quartz"--special crystals that have split along certain planes indicative of a large impact--immediately beneath the Deccan Traps of India. The Deccan Traps are areas of huge volcanic deposits that have been dated to 65 million years ago, the time of the dinosaur extinction, so findin
'"/>

Contact: Jonathan Sherwood
jonathan.sherwood@rochester.edu
585-273-4726
University of Rochester
20-Nov-2003