What are asteroids?
Asteroids are rocky objects primarily found in the asteroid belt, a region of the solar system that lies more than 2 ½ times as far from the Sun as Earth does, between the orbits of Mars and Jupiter. These objects are sometimes called minor planets, and are likely the leftovers of the solar system’s planet formation. Thousands of asteroids have been discovered, ranging in size from tens of meters to hundreds of miles across. Despite their number, the total collective mass of discovered asteroids is still far less than the mass of the Earth.
Asteroid Encounters with Earth
Asteroids that fall into the category of Near Earth Objects have orbits that bring them in close proximity with our planet, and a number of notable impact sites have been attributed to asteroids. Most famously, the Chicxulub crater under the Yucatán Peninsula in Mexico is the result of an asteroid impact that might have wiped out the dinosaurs. Another asteroid known as Tunguska didn't impact Earth, but exploded a few miles above the Podkamennaya Tunguska River on June 30,1908. A similar explosion made headline news in 2013, when the near-Earth asteroid dubbed Chelyabinsk exploded in air blast that left 1,500 Russians seeking medical attention.