Washington, 23 November 1998 (RFE/RL) -- An American scientist says that a fragment of a meteorite smaller than a fingernail is the first hard evidence that catastrophic space debris slammed into the Earth more than 65 million years ago and may have caused the extinction of dinosaurs and other life.
American geochemist Frank Kyte of the University of California at Los Angeles (UCLA) made the statement last week in a report published in Nature, a prominent U.S. science journal. Kyte, whose research was funded by the U.S. National Science Foundation, says he believes he has found the first-known fragment of the deadly meteorite that collided with Earth.
Some scientists believe the extinction of the dinosaurs -- which ended the Cretaceous period 65 million years ago -- came about because of the destructive impact of a meteorite. They say the impact, which was believed to have hit near Mexico's Yucatan peninsula, was so intense that debris and dust rose into the atmosphere blocking the sun and upsetting the world's climate. Those species that survived the initial blast most likely died out as important food sources disappeared, they add.
Kyte writes in his study that the meteorite was probably more than nine kilometers wide and sped toward the Earth at about 64,000 kilometers per hour. He says he found the meteorite fragment buried deep beneath the Pacific Ocean while studying the sediment boundary layer between the Cretaceous and Tertiary eras. Because it had been buried there for millions of years, the fragment was no longer composed of all its original minerals, but had still retained its shape and texture.
Kyte says he was able to deduce the meteorite's origins by using instruments from the electron microprobe and neutron activation laboratories at UCLA. The fragment contained high levels of iridium, a rare element on Earth, but one found in abundance in meteorites.
Richard Lane, a paleontologist and program manager of the study at the National Science Foundation, told RFE/RL that Kyte's findings are exciting.
Says Lane: "His findings are very important because they really provide the first hard evidence of a theory that had yet to be proved with physical evidence. It's another piece of the puzzle in the history of the Earth."
But Lane says there is still a hot debate among scientists as to whether the meteorite impact is what caused the dinosaur extinction or whether it was something else.
Lane says scientists have determined that the dinosaurs were already going through a progressive reduction in their numbers before the meteorite even hit. He says dinosaurs were likely already being adversely affected by the large number of volcanoes which were exploding and an unstable terrain that was shifting as the Earth experienced a period of mountain building.
Says Lane: "It is thought by some people that the meteorite impact was simply the coup de grace for the dinosaurs. It was a catastrophic event, but it wasn't necessarily the only thing that lead to extinction of the dinosaurs. But it applied the final tap."
Lane says that Kyte's work has shown that celestial impacts can have just as an important effect on the history of the Earth as did more gradual processes.
He adds: "Remember, major catastrophic events like this, although they may be a death knell for the dinosaurs, ended up being an opportunity for another group of life -- the mammals.