Scientists have found evidence of a huge crater under the Caribbean that may be the ``smoking gun`` to support the theory that dinosaurs and other species were wiped out by a meteorite that struck Earth 65 million years ago.
Reported in Friday`s edition of the journal Science, the discovery, if confirmed, would answer one of the biggest arguments against the ``impact- extinction`` theory for the demise of the dinosaurs.
Confirmation could have ``just an electric effect on the scientific community,`` said David Raup, a paleontologist at the University of Chicago, who has written extensively on the theory.
Scientists` inability to find a crater caused by the supposed impact has been a major weakness in the theory that the impact of a large asteroid or comet caused one of the greatest extinctions of life on this planet, the so- called Cretaceous-Tertiary extinction.
But Alan Hildebrand and William Boynton of the University of Arizona say considerable evidence now points to an impact somewhere in the Caribbean Sea, where a 180-mile-wide circular formation lies buried under a mile-deep layer of sediment in the seafloor off the coast of Colombia.
Much of the evidence is based on deposits from that period found in Cuba and Haiti that show signs of a huge tidal wave triggered by an impact that occurred within a range of about 600 miles.
Hildebrand and Boynton also say the chemical composition of sediment debris strewn around the world at the time of the impact indicates the meteorite landed in the ocean, not on dry land.
Most of the sea floor within 600 miles of the Caribbean site has been well-studied and shows no signs of a crater, they say. But the region just off the South American coast has not been as well mapped, and that is where they have found signs of a crater twice as big as any known impact crater on Earth.