March 11, 1998

It's only been two months since Lunar Prospector blasted off on its five-day journey to Earth's "backyard neighbor." But the small, cylindrical spacecraft is already putting to rest questions that have plagued lunar scientists since the days of the Apollo missions.

Prospector has found somewhere between 10 and 300 million tons of water ice in the lunar north and south pole areas. Twice as much of the water ice mixture detected by Prospector was at the Moon's north pole, a surprise to many scientists. But Prospector scientists can't yet determine how many craters at the two poles contain the water ice measured. Another instrument aboard the spacecraft, the gamma ray spectrometer, will help mission scientists sort out the precise distribution of the lunar ice in the months to come.

The search for water ice on the Moon is based largely on one instrument aboard Prospector, the neutron spectrometer. This instrument detects small particles of energy, called neutrons, which continually arise from the lunar surface. There are three neutron ranges that the instrument can detect: low-energy "thermal" neutrons, medium-energy "epithermal" neutrons, and high-energy "fast" neutrons. The key to finding a water ice signature with this technique is to monitor how each neutron type interacts with wet lunar soil and with dry lunar soil. Lunar soil containing water (and therefore an abundance of hydrogen ions) is much better at "moderating" (slowing down) medium- and high-energy neutrons.

Scientists guess that most of the water ice may have come from meteoritic and cometary impacts.

The detection of water ice on the Moon could have great economic potential as a supporting resource for future human exploration of the Moon and the solar system. If a lunar base is established, water on the Moon could dramatically reduce the cost of the creation of a lunar base.

For example, a typical person consumes an estimated 100 gallons of water per day for drinking, food preparation, bathing, and washing. At that rate, an estimated 33 million tons of water (7.2 billion gallons) could support a community of 1,000 two-person households for more than a century on the lunar surface, without recycling. A spaceport on the Moon could be closer than we think!

Prospector is scheduled to continue its current primary data gathering mission at an altitude of 62 miles (100 kilometers) for 10 more months. Then, the spacecraft will use its rockets to drop to an orbit of approximately six miles (10 kilometers), collecting data at a much finer resolution for more detailed lunar studies. When Prospector finally runs out of fuel, probably six months later, it will crash on the lunar surface.

*Special thanks to Aaron Stout and Valerie Kelley, Fairmont Senior High, for their contributions to this Observation of the Week.

More Cool Stuff

NASA's Lunar Prospector homepage. It is filled with up-to-the-minute happenings and is your best source of information:

http://lunar.arc.nasa.gov/

For information about the Galileo flybys of the Moon, check out:

http://galileo.ivv.nasa.gov/

To learn more about Lunar Prospector's mission, check out the Observatorium's own article on the spacecraft at:

http://observe.ivv.nasa.gov/nasa/space/prospector/lunar1.html

Teachers, try the Observatorium's teacher's guide to our Prospector article. It's filled with handy helpers, including classroom activities, a quiz, related topics and links, and a summary.

http://observe.ivv.nasa.gov/nasa/education/teach_guide/lunar.html

As part of its Learning Technologies Project (LTP), NASA supports a number of educational Web sites that have excellent material on the space sciences:

Windows to the Universe, an innovative and engaging Web site about the Earth and space sciences.

http://windows.ivv.nasa.gov/

Science Information Infrastructure provides access to Earth and space science data through the nation's science museums.

http://www.cea.berkeley.edu/Education/SII/SEGway/