WASHINGTON -- NASA is planning to smash the moon with a used spacecraft next week in a search for ice, but two scientists predict it'll turn up only a concrete-like layer of lunar soil and no water.
The $63 million Lunar Prospector mission concludes Aug. 1 and researchers plan a spectacular end for the little spacecraft -- smacking it into a constantly shaded crater on the moon's South Pole.
National Aeronautics and Space Administration researchers believe there is a good chance the 3,800-mph (6,115-kph) crash of the 354-pound (160-kilo) craft will gouge a hole in the crater deep enough to free a cloud of water vapor if ice is locked in the frigid soil.
Scientists are eager to find water on the moon because it can be chemically reduced and used as a rocket fuel and as a breathable gas. The presence of water would make it possible to build a base on the moon without the need for fuel and oxygen resupply from Earth.
But Von R. Eshleman and George A. Parks, researchers at Stanford University, said in a letter to the journal Science that Lunar Prospector is more apt to collide with a concrete-like mineral inside the crater than ice.
``We don't believe that crater is paved like a roadway, but we do believe the soil may be chemically very much like concrete,'' Eshleman said in an interview.
If there is water on the moon, Eshleman said, it is probably in the form of hydrous, or water-containing, mineral crystals.
Hydrous minerals do contain water, but it is so tightly bound chemically to the crystals that it would take temperatures up to 1,500 degrees Fahrenheit (815 Celsius) to break those bonds and extract useful water, he said.
Eshleman agrees with NASA scientists that if there is any water on the moon -- a highly uncertain possibility -- it is probably in the soils in deeply shaded craters at the lunar poles. But once the water got trapped there, he said, it is very likely the water combined with the dry lunar soil to form the crystal minerals.
David Goldstein, a University of Texas researcher who first suggested smashing the moon with the Lunar Prospector, conceded that some lunar water may be chemically locked in minerals, but he thinks there also might be ice.
``We think the chances of there being free water there is about 10 percent,'' he said.
Goldstein said the energy released by the Lunar Prospector's crash into the moon will vaporize ice, but not separate water from the minerals.
``In a half cubic meter of soil, the crash will raise the temperature by about 400 degrees Kelvin (about 720 F or 382 C),'' said Goldstein, far less than the 1,500 degrees F needed to extract the water from a concrete-like crystal.
This means that if any water is detected from the collision, it probably came from ice, not from hydrous minerals, said Goldstein.
Lunar Prospector was launched Jan. 6, 1998 and has spent 18 months orbiting the moon. It used instruments to map the lunar surface, plot the moon's geology and search for water.
Lunar Prospector will smash into one such shaded crater at about 5:52 a.m. EDT on July 31.
``We selected that day because the funding for Lunar Prospector runs out on Aug. 1,'' said Goldstein, a member of the spacecraft science team. ``We thought this would be a good way to end the mission and still get some science.''
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