Comet Impact
Written by Jerry Coffey
The chance of a comet impact are 100%. The big question is when? Every object in the Solar System shows evidence of multiple impacts. The Earth has over one hundred verified impact craters and several more that have not been verified as of yet. The most recent was in 2008 when a small object hit our atmosphere. It burned up immediately and left nothing to hit the ground, but it goes to show that these events happen on a yearly basis.
Small objects hit the Earth with an amazing regularity. Astronomers have even gone to the trouble to predict these comet impact events. Objects with a 1 km diameter impact the Earth every 500,000 years on average. Large collisions with five kilometer objects happen approximately once every ten million years. Objects with diameters of 5-10 m impact the Earth's atmosphere approximately once per year, but break up and most of the material is vaporized in the upper atmosphere. Objects of diameters of over 50 meters strike the Earth approximately once every thousand years. It is easy to believe these numbers when you take into account the millions of objects that are out there, then couple that with gravity anomalies, etc. The surprise is actually that you would expect more frequent impact events.
Comet impact events help us to learn more about space born objects and their content, but could be very dangerous for the peoples of the world if we are caught off guard. The complexity of the SENTRY and NEAT programs will prevent any unexpected strikes and will help us to defend any threatened cities. The movies have embellished on what might happen to prevent an impact, but they might not be too far off from the truth.
There is a nice article on NEA monitoring here. Here on Universe Today there is a great article on a recent comet impact event on Jupiter. Astronomy Cast has a good episode on ice in space and death from the skies. Enjoy them all.
Filed under: Astronomy
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