 The first landing on an asteroid was performed by the "NEAR Shoemaker" probe in 2000, following an orbital survey of the object.The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, were visited by NASA's "Dawn" spacecraft, launched in 2007.Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited.