When scientists announced last March that the Lunar Prospector spacecraft had detected evidence of as much as 300 million tons of water at the moon's poles, advocates of space travel were ecstatic, envisioning moon colonies with ready-made reservoirs. To find the water, which astronomers believe came from comet impacts billions of years ago, Prospector has searched the lunar poles since January.
Neutrons lose predictable amounts of energy when they bounce off water's hydrogen atoms.
Prospector indeed saw fewer such neutrons near the lunar poles, a sign that water was present. The deep purple parts of this false-color image of the moon may show where ice exists. Most of the water, he says, sits 16 inches below the lunar surface. Solid pieces of ice would be much easier for astronauts to extract than frost would be, says Lawrence. They're also better for research.