The origin of the Moon is usually thought to be that a Mars-sized body struck the Earth, making a debris ring that eventually collected into a single natural satellite, the Moon, but there are a number of variations on this giant-impact hypothesis, as well as alternate explanations, and research into how the Moon came to be continues.[1][2] Other proposed scenarios include captured body, fission, formed together (condensation theory), planetesimal collisions (formed from asteroid-like bodies), and collision theories.[3]