Asteroid: A relatively small, inactive, rocky body orbiting the Sun. Comet: A relatively small, at times active, object whose ices can vaporize in sunlight forming an atmosphere (coma) of dust and gas and, sometimes, a tail of dust and/or gas. read more
Blair noted that a 1000-meter-diameter asteroid in that class could provide platinum worth $690 billion, assuming complete recovery of platinum. John S. Lewis, professor of planetary science and author of Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets, takes it much further. read more