This composite image shows the comparative sizes of nine asteroids. Up until now, Lutetia, with a diameter of 81 miles (130 kilometers), was the largest asteroid visited by a spacecraft, which occurred during a flyby. Vesta dwarfs all other small bodies in this image. Asteroid Vesta also is considered a protoplanet because it’s a large body that almost became a planet and has a diameter of approximately 330 miles (530 kilometers). Image Credit: NASA/JPL-Caltech/JAXA/ESA