The Falcon Has Landed

Killer asteroids are the stuff of science fiction movies, but the threat from near-Earth asteroids, at least in the long term, is real. Asteroids are small solid bodies, hundreds of meters to many kilometers in size, with rocky, perhaps icy, surfaces. Understanding of what and how they are built may not only someday help us deflect or destroy one on a collision course with Earth, but tell us how Earth was formed. Asteroids preserve within them detritus left over from the debris disk out of which the planets grew some 4.5 billion years ago. Since then, most asteroids have suffered collisions and impacts and often show the scars. Some can even be linked to collected meteorites that were ejected as a result.