Scientists think they found the smoking gun to show that asteroids wiped out the dinosaurs: a 110-mile-wide crater in Mexico possibly gouged by a mountain-size rock smashing to Earth.

The crater near the Yucatan Peninsula town of Chicxulub may have been "ground zero" for the collision that some scientists believe killed dinosaurs 65 million years ago, University of Arizona scientist Bill Boynton said Tuesday.The collision, with the estimated power of 70 million one-megaton bombs, could have kicked up 3-mile-high tidal waves and a sparked a worldwide firestorm.

"We think we have found the smoking gun, but there may be other guns and maybe a firing squad," Boynton said during a meeting of the American Geophysical Union.

Boynton and other researchers said another impact crater 22 miles wide near Manson, Iowa, and possible craters under the Caribbean near Colombia and Cuba point to the possibility a shower of asteroids or comets caused the extinction.

The Yucatan crater Boynton and his colleagues theorize was caused by an asteroid striking shallow Mexican waters is now on dry land, buried by 65 million years of sediment.

The study by Alan Hildebrand, Boynton and others was the latest of more than 2,000 in the past 12 years that examined whether asteroids, huge volcanic eruptions or slow climate change sent the dinosaurs to oblivion.