Ever wonder what would happen if the Earth were ever really threatened by an incoming asteroid just like in the movies? Well, some in the European Space Agency have been thinking about it, too. In fact, they have given high priority to a Spanish project that aims to crash two spacecrafts into an approaching asteroid to see if they can alter its path— just to make sure we're prepared for anything that might be coming our way someday in the future.

Just what are asteroids? The largest non-planetary or non-lunar objects in the solar system, asteroids are objects in space larger than 100 meters, or 1 kilometer, in diameter. The vast majority of asteroids (94 percent) are found between Mars and Jupiter in the asteroid belt. All together, the asteroids amount to a total mass of only 1/1600 that of Earth and are apparently just debris left over from the formation of the solar system.

Other groups of asteroids exist elsewhere in the solar system. The Apollo asteroids (also called Earth-crossing asteroids or near-Earth objects) have orbits in the inner part of the solar system. These asteroids number a few dozen and are mostly about 1 kilometer in diameter. Astronomers believe that one of these small bodies likely will hit Earth every million years or so.

To find out more about the so-called Don Quixote mission and the spacecrafts named after the fictional adventurer and his sidekick Sancho Panza, check out this article from Space.com.