
Arizona's Meteor Crater and other scars leftover from collisions with space rocks continue to serve up their secrets.
Meteor Crater formed some 50,000 years ago. It represents the best preserved meteor impact site in the world, measuring some 700 feet deep (213 meters), more than 4,000 feet across (1,219 meters), and 2.4 miles (3.9 kilometers) in circumference.