Asteroids are rocky-metallic objects which range in size from about the size of pebbles to around 1,000 km across. Although they orbit the Sun, they are too small to be considered planets. When asteroids enter Earth’s atmosphere, they become meteors. After they hit the ground, they are called meteorites.
At a recent panel of the Association of Space Explorers (a professional organization for crew on space flights) in New York, the five astronauts said there are about 10,000 known asteroids orbiting our region of the solar system – that’s just one-thousandth of the number scientists believe could actually be there, and only 1 percent of potentially dangerous asteroids have been detected by ground-based telescopes. They said governments around the globe should urgently help fund the launch of a space-based infrared telescope that can detect the heat emitted by asteroids, map their position and orbit, then provide a warning in time to mount an international effort to deflect the more dangerous ones.
The meteor that exploded on February 15 of this year over Chelyabinsk, Russia injuring around 1,200 people, mostly from the blinding flash, skin-peeling sunburns, and from shattered window glass by shock wave, measured only around 17 -19 meters wide.
They also emphasized the need to include asteroids in national disaster plans and budgets, and to designate each country’s agency in charge of responding to asteroid threats. Once spotted, a potentially devastating asteroid could be pushed off a collision course by a spacecraft. Their proposed defense system could prevent an asteroid of up to 400 meters in diameter from striking the earth. For an even larger one, multiple rockets could be used to fragment it. The astronauts warned that an asteroid over 150 meters in diameter falling into the sea would likely cause a tsunami.