Of the many threats posed to life on Earth by objects from outer space, meteors have a history of killing before and can do so again without warning.
We can thank a deadly meteor for our life on Earth. If it weren't for the meteor that smashed into the area of the Yucatan Peninsula 65 million years ago, the dinosaurs and other large creatures wouldn't have become extinct and humans may have had a real difficult time in their fight for survival. But meteors are random rocks sailing through the solar system. They can hit at any time, wiping out the new dominant species on Earth and creating a whole new hierarchy. Meteors don't play favorites, and an advanced warning is not a given.
One of the big tourist attractions in Arizona is the Barringer Meteorite Crater outside of Winslow. The crater spans almost a mile in width and drops down to a depth of 570 feet. The meteor that scarred Arizona was estimated to be about 150 feet across when it struck approximately 50,000 years ago. But there is damage that is more recent than Barringer Crater.
The last large meteor to enter Earth's atmosphere occurred less than 100 years ago. On June 30, 1908, a meteor sped toward Earth at such an angle that it entered the atmosphere in an area over Siberia, causing an explosion, but continuing on out into space. In essence, it skipped across our atmosphere like a stone on a smooth pond. Fortunately, the region, known as Tunguska, is sparsely populated and no one was killed in the explosion, which leveled 500 square miles of forest.
Another meteor gave a glancing blow to Earth's atmosphere even more recently. On August 10, 1972, the blue sky above the gorgeous mountain scenery in Grand Teton National Park was pierced by a meteor that was captured on video sailing across the sky. The object was later estimated to be approximately 10 meters wide and several thousand tons in weight.
Meteors have even struck the same place twice. In 1971, a meteor crashed into a home in Wethersfield, Connecticut, population 26,271. In 1982, a meteor again crashed into a home in Wethersfield a mile from the '71 impact.
Spacewatch is one of the programs working to map all the space rocks in the solar system that may prove dangerous to life on Earth. So far, in 2006 alone, Spacewatch has detected 205 PHAs, or Potentially Hazardous Asteroids. Scientists have even developed a scale for ranking the perceived danger of PHAs. The Torino Scale was devised during a conference in the city of the same name. The Torino Scale ranks objects from 0 - meaning no chance of impacting Earth, to 10 - meaning the collision is certain and large enough to have global consequences. The current highest values for any near-Earth object is one, which gives it an unlikely chance to impact with Earth. This would be comforting if we had located and were tracking a majority of the objects, however of the 1 million-some space rocks believed to be in our vicinity, we have a long way to go.
View video of meteors that have burst through Earth's atmopshere.
