Early solar system. Computer artwork showing how the newly formed Earth (lower left) and Sun (upper right) may have appeared shortly after the Sun's heat and solar wind cleared the inner solar system of cooler gases. The entire Earth is molten due to radioactive heating and frequent heat-generating collisions with debris left from the solar system's formation. Thousands of icy comets can be seen swarming around the Sun. Some of these comets will eventually collide with the Earth and other planets, delivering water and other rare materials to the fledgling worlds.