 At one time, it was thought to be the biggest impact by an object from outer space in North America, until subsequent studies revealed larger examples.The impact event was also once theorized to have led to the extinction of the dinosaurs, or contributed to it as a fragment of the Chicxulub meteor, until tests by the U.S. Geological Survey in 1991 and 1992 proved that it was too old by 9 million years.Not much remains due to glacial till which has filled in the crater and has made it undetectable at ground level.