dipper@utastro.UUCP (Debbie Byrd) (06/19/85)
Meteor Crater in Arizona was formed when an object from space struck the Earth. More -- after this. June 19: When Worlds Collide What would happen if a comet or asteroid stuck the Earth? Well -- lots of them already have. Dozens of craters -- like what you see on the moon -- have been identified on Earth. They were caused by the impact of objects from space with the Earth -- most of them thousands or millions of years ago. Most have been badly damaged by erosion. But a well preserved crater can be seen near Flagstaff, Arizona. This hole in the ground is three-quarters of a mile wide and as deep as the length of two football fields. It's called Meteor Crater. Meteor Crater is about 20 thousand years old. Most scientists believe it was formed when an asteroid struck the Earth, since more than than 25 tons of iron fragments have been found in and around the crater. When a very large object from space strikes the Earth, it can have world-wide effects. Recent evidence suggests that the dinosaurs may have disappeared from the Earth because of a climate change caused by the impact of an asteroid 10 or 20 miles in diameter -- which crashed into the Earth at 20 or 30 miles per second -- 65 million years ago. Such an event might produce clouds cutting off sunlight from the ground for months or even several years -- a natural effect similar to the "nuclear winter" predicted by scientists to be an outcome of nuclear war. No one knows when the next large asteroid will strike. But the subject is important -- and some astronomers are studying objects in space with orbits crossing that of Earth. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin