Introduction

NASA's Lunar Prospector has gathered a wealth of data since it began orbiting the moon in January 199, including further evidence of water. The big news is that scientists now estimate 3 billion metric tons of ice are located at each of the moon's poles. That is larger than scientists first estimate of 350 million metric tons. "As of March, we were sure we were seeing hydrogen, but we had to clean up the data," says William Feldman, a laboratory fellow at Los Alamos National Laboratory, who led the study on Prospector's search for water on the moon.

Still, he does admit the estimate is still "a wild guess" since it's still uncertain over how wide an area the ice covers and how pure it is. "There are a lot of assumptions going into that number," Feldman says. NASA says that it will know for sure until it sends a mission to the moon to dig. Highlights from the information Prospector has collected were published recently in the journal Science. The water, in the form of ice was probably brought to the moon on the tails of comets or asteroids, and is buried between 1.5 feet and 6 feet beneath the surface.

Previous Evidence

This finding differs from data received from the spacecraft Clementine, which first indicated the possible presence of water on the moon. Clementine's findings published in November 1996, showed less water than is now thought to exist. It appears now that the Clementine signalÑwhich was disputed by radar measurements from Earth, may have just been a quirky data point. For the distortion to occur, you need yard-long pieces of almost pure ice. What Lunar Prospector has been detecting, is smaller ice crystals dispersed in the soil several yards down. "Neither the Clementine or the Arecebo radars would have seen that," says Donald Norman, a Cornell University astronomer who wrote a paper in Science last year disputing the Clementine results. "We don't have any particular argument with that (the Lunar Prospector findings) at all. It sounds exciting that there might actually be something there."

The presence of water on the moon is important if the moon is ever going to be colonized or used as a stopping-off point in exploring planets. It would be less expensive by far if we could live off the resources that are found on the moon instead of having to send everything up via the space shuttle and other rockets. NASA will get a chance to further check these findings when Prospector dips from its current altitude of 63 miles to an orbit of just six miles above the moon in January.

Specifications

The Lunar Prospector spacecraft is a cylinder, about 5 feet in diameter and 4 feet tall and weighs about 650 pounds. Its engines need to be fired only once every 56 days to correct its orbit. Prospector has no on-board computer, only an electronics box that executes commands it receives from a team on Earth. "It's a very stupid spacecraft which is great because nothing ever goes wrong," says Alan Binder, director of the Lunar Research Institute and designer of the Lunar Prospector Mission.

The spacecraft's simplicity also has benefits for the research, since it produces little background noise to interfere with the scientific experiments. Prospector is mapping the entire moon, determining the concentrations of elements that make up the moon. The Apollo missions only mapped about 25 percent of the moon, in the areas around the moon's equator.

Prospector houses five separate scientific instruments which, in addition to the mapping and the search for water, have been relaying information about the moon's gravity and its magnetic field, which may have been caused by the impact of comets. Prospector is traveling at a speed of 3,669 miles per hour. It circles the moon about once every two hours. The mission cost only $63 million and is part of NASA's Discovery Program. This program funds space missions planned by an independent groups to keep down space exploration costs and is capped at $150 million for Discovery missions.

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