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What is an Impact Event?

August 13, 2013

Hi, my name is Emerald Robinson, and in this “What is” video, we’re going to discuss the collision of two objects from outer space, known as an “Impact Event.”

An “Impact event,” refers to what happens when any two celestial objects hit each other. Most of the time, though, we use the term to describe what happens when a comet, meteor, or asteroid hits the earth or the moon. Astronomers call this group of objects that cause impact events “bolides.”

When bolides enter the earth’s atmosphere, they do so at high rates of speed, between 25 and 160 thousand miles per hour. Most bolides disintegrate, burning up as they move through the earth’s atmosphere.

If a bolide makes it through the atmosphere and strikes the earth, it does so with an enormous force, one equal to thousands of tons of dynamite. This force causes a depression called an impact crater.

Although impact events may seem to be the stuff of science fiction, bolides with diameters smaller than 13 feet actually hit the earth about once a year. We just don’t always hear about them because so much of the earth’s surface is covered with uninhabited land or open ocean.

Some impact events have had major consequences for the earth. One of the most well-known is the “cretaceous-paleogene” event, which occurred about 65 million years ago. During this event, scientists think a meteor about 6 miles across struck the earth on Mexico’s Yucatan peninsula, forming the 110 mile wide Chicxulub impact crater, and causing the extinction of about 75% of animal and plant life, including most of the dinosaurs.

While we don’t know for sure if there will be another major impact event, scientists at NASA use a system called “Sentry” to monitor known celestial objects and calculate the likelihood of every potential impact event.



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