Far More than a Hole in the Ground


The simulator at the Meteor Crater Museum really did look like that—complete with arcade game buttons that allowed you to end worlds. Earth, the Moon, and Venus were the available targets for bombardment from comets and both rocky and nickel-iron asteroids. Once a combination of factors was entered, a little video played, displaying what the impact crater would look like. Crank everything up high enough, and you could reduce the moon to cinders. Ancient death machine aside, the museum was really great. It featured exhibits on everything from the changes to local geography to the latest efforts to find and catalog near Earth objects.

When Meteor Crater was first beginning to be studied, it was believed to be volcanic in origin. In fact, during our walk through the museum, I learned just how tricky it can be to differentiate a volcanic crater from one caused by an impact*. While Daniel Barringer first suggested that the crater was caused by a meteor in the early 1900s—noting the existence of pulverized silica, meteoric material, and complete lack of volcanic rock in the area—it wasn’t until the 1960s when geologists such as Eugene Shoemaker showed that the rocks and deformed strata around Meteor Crater bore striking resemblance to those found after underground nuclear bomb tests. Shoemaker pointed out that the sort of heat and pressure shock that the local strata underwent was consistent to that of a high speed impact. Amongst the museums many specimens were samples of highly shocked rocks, microscopic diamonds formed by the intense heat and pressure, and tektites, which are small beads of natural glass formed by high energy impacts.

Despite the evidence suggesting a meteor impact, Meteor Crater lacked a smoking gun—or in this case, a smoking hot chunk of meteorite. Barringer himself had funded several drilling operations on the floor of the crater. He was certain that the meteor that struck the Earth must have been ten million tons. He dug downwards, hoping to find the massive object that caused the crater. Unfortunately, the mine shaft had to be abandoned when it hit the water table and turned to quicksand (Yikes!). Desperate to find something, the team consulted astronomer F. R. Moulton, who broke the bad news: Given the size of the crater, and the energy at which it struck, the object Barringer was looking for was likely only 300,000 tons in mass, and it had probably vaporized on impact. Visitors to the crater can still see the abandoned mine shaft at the bottom of the crater.

Later exhibits turned our eyes to the stars and Lowell Observatory’s Near-Earth Object Search. Located in nearby Flagstaff, Arizona, the observatory scans the skies every night and takes photographs. A computer then analyzes the photographs and looks for movement in the skies. Finding and cataloging our wandering neighbors is our best defense against future impacts. The more warning we have of approaching objects, the better we can act against them.

If you really want to be terrified, check out this video by astronomer Scott Manley, which shows all the near-Earth objects discovered since 1980:

*I pretty much failed the quiz.