An asteroid is a roc in orbit around the sun. The asteroid belt is located between Mars and Jupiter, and contains possibly until a few hundred thousands ones. It happens sometimes that some of them cross the neighbours of the Earth, as it has been the case in 2004. Many theories suggest that the asteroid that crashed some millions years ago in Arizona would be the root cause of the extinction of the dinosaures. The american robot Near has been satellized around the asteroid Eros on the 14th of February, 2000. A robot of this mission touched also this asteroid on the 12th of February, 2001.