Everyone has a secret fear that the Earth will be destroyed by an Asteroid impact, right? On February 28th, Bill Cooke, a member of NASA’s Meteoroid Environment Office, delivered a presentation on the threat of asteroids to Earth. Cooke began his talk with a description of the Asteroid Belt. Unlike the jam packed area seen in standard science fiction movies, the actual asteroid belt is 500 million miles wide and contains thousands of asteroids spaced about a million miles apart. These asteroids can be classified by their contents into six different types (C – Carbonaceous, S – pyroxene and olivine, D/P – primitive, M – Iron, and E – Enstatite). The terminology of the asteroid also changes based on its size and location. Meteoroids are chunks of rock and ice out in space which are about the size of a boulder. Meteors are meteoroids that disintegrate in Earth’s atmosphere, while meteorites are what is left of a meteoroid if it makes it to the surface of the Earth. Cooke even explains how to classify meteors based on their brightness. Fireballs are meteors that are brighter than Venus, and Superbolides are meteors that are brighter than a full Moon.
All of this information becomes important once Cooke gets into the nitty gritty of his discussion on history’s famous meteorite falls. There have been several recent events including the meteorite falls in Peekskill, NY in 1992, in Park Forest, IL in 2003, as well as the February, 2013, Chelyabinsk meteorite. The Chelyabinsk meteorite didn’t strike anyone, but over 1600 people were injured from associated glass and debris. However, there HAVE BEEN examples of people being directly struck by meteorites. A record exists of a friar being killed by a “stone from the clouds,” and in 1992 a small boy in Uganda was hit by a small fragment and was not injured.
Cooke then talked about how there have only been four major meteorites throughout history (Chelyabinsk included) that have actually caused significant damage. The danger from meteorite impacts is quite small, and there are people protecting us from these rocks. Yes, we would all love it to be Superman, but alas it is just a group of scientists! Scientists at NASA have conducted many different surveys on the rocks floating around in space. The International Asteroid Warning Network (IAWN) and the Space Missions Planning Advisory Group (SMPAG) work together to determine the impact time, location and severity of asteroids, as well as potential deflection mission plans. The U.S.’s policy current policy is to attempt to deflect any meteoroid larger than 50 meters. For smaller impacts, our plan is just to evacuate the impact zone. So all of this being said, your irrational fear of being hit by a meteor should be calmed! The scientists are protecting you.
Cooke, B. 2018. The Asteroid Threat to Earth. NASA Technical Reports Server: M18-6549.