Samples of the Moon, returned to Earth as a result of the _______________ mission, show that the Moon has a much lower contents of water and other ______________ materials. More recently, during the _____________ mission, NASA crashed a small
spacecraft into a crater near the Moon's ___________ A plume of water and other materials
was blasted outward and could be measured.
Astronomers estimate that hundreds of billions of tons of frozen water can be found on the Moon, brought there by_______________ and shielded from sunlight in ______________.