About 4.5 billion years ago, a Mars-sized object, named Theia, slammed into a proto-Earth to create the Moon.
A recent discovery suggests Mars may have once had a much larger moon, which could have caused tides in a lake that once filled Gale Crater. This intriguing possibility comes from a study of sediment ...
The moon is Earth's only natural satellite, a rocky celestial body that orbits our planet at an average distance of about 384 ...