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Killer Asteroids (2004)

385543 / Apr 9, 2017


Killer Asteroids (2004) NatGeo

We live in a very dangerous corner of the universe. Millions of lumps of rock (some tiny, some the size of Texas) often cross our planet's path. Add to that numerous comets and the odds of a collision are 1-in-20,000 by the end of the century. Where can we find evidence of previous collisions? Try Meteor Crater in Arizona. A mile across, it was formed 50,000 years ago when a 150-foot rock slammed into Earth. The collision generated heat ten times hotter than the sun. Under these conditions, a unique shocked quartz mineral is formed, leaving a clear calling card as to what happened. Manson, Iowa is the present-day site of one of the biggest impacts ever known. Core samples taken there in the 1980s revealed shocked quartz. A crater over a mile across was formed, but today there's no visible trace thanks to the erosive qualities of wind, rain and ice. The largest impact known was in the Yucatan peninsula 65-million years ago. The asteroid was over six miles across and blasted vaporized rock half way to the moon. Some scientists believe the sun was blocked by all the dust, disrupting the food chain and bringing about the death of the dinosaurs. On the upside, the stage was set for the arrival of mammals. What's being done to protect us from a future impact? NASA has begun searching the skies and even sent a probe (Deep Impact) to rendezvous with comet Tempel 1. In the movies, Earthlings just detonate a nuclear bomb on an asteroid and it goes away. That won't work, however, since most asteroids are groups of smaller rocks held together by gravity. A blast would only temporarily separate them--and turn them radioactive. A better idea being considered is sending an 'asteroid tugboat' that would gently pull the rocks into a different direction.

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