RigBJRE9oFdCxR — 2022-02-17 13:17:04 UTC Chief among them is whether Mars ever had the right conditions to support small life forms called microbes. The moon is rotating at the same rate that it revolves around Earth (called synchronous rotation), so the same hemisphere faces Earth all the time. Even though Ceres comprises 25 percent of the asteroid belt's total mass, tiny Pluto is still 14 times more massive. From an average distance of 1.8 billion miles (2.9 billion kilometers), Uranus is 19.8 astronomical units away from the sun. Ceres is a good example of how challenging it can be to categorize bodies in our solar system.