Prospector spacecraft to smash into moon Saturday

Artist's conception of Lunar Prospector on its final descent QUICKTIME NASA animation of the Prospector crash 45 sec. 5.7mb QuickTime movie Please enable Javascript

July 30, 1999
Web posted at: 9:54 a.m. EDT (1354 GMT)

(CNN) -- Decades after the first Mercury capsules splashed down in the Earth's oceans, NASA hopes for a lunar splashdown Saturday when a robotic spacecraft takes a controlled dive into the moon's south pole.

Last year, early in Lunar Prospector's moon mapping mission, scientists said they found indirect evidence of moon water lurking in countless dots of ice crystals sprinkled throughout the lunar surface.

Even more water ice, which theoretically could be converted to rocket fuel someday, is thought to be present at the moon's shady poles.

Alan Binder, who heads up the $63 million mission, hopes to get his first direct evidence of water just after 5:51 a.m. EDT when the 158 kilogram (327 pound) spacecraft is intentionally smashed into a crater the size of a small city.

Binder believes the target crater is filled with water ice.

"The trick is that we want to find out if it's really water that we're mapping," Binder says.

If Binder is right, the spacecraft's impact at 2,356 km/h (3,800 mph) will throw up a huge plume of water vapor and rock debris that could be seen for hours by instruments at the Keck Observatory on Mauna Kea, Hawaii, and other telescopes such as the Earth-orbiting Hubble Space Telescope.

"Then we don't have to say that we infer water," Binder says. "We will know that it's water that we found."

The hitch is that the idea has a low probability of success -- about 10 percent, Binder says.

Instruments on Prospector can only see targets 60 kilometers across so it'll be tough to hit a crater half that size. Next, Binder is unsure exactly where the water is. The crater is just his best guess.

"We know it's down there somewhere," Binder said. "It might be spread all over the place."

Finally, the craft will strike the moon at a shallow six-degree angle. If it hits a tall rock first before arriving at the crater, it will miss the water.

"Clearly I'm going to crash the spacecraft anyway," Binder says. "We're trying to do the most useful thing scientifically."

The launch of Lunar Prospector in January 1998 marked a revival of American exploration of the moon. Before that, NASA had not sent any explorers -- human or robotic -- to the moon since 1972.

The goal with Lunar Prospector has been to do what previous missions left undone by mapping of the entire lunar surface and closely analyzing the moon's composition.

Already, the mission has yielded five global maps, including a gravity map, a magnetic map, and the water, or at least, hydrogen map.

Prospector also has mapped the location of 12 elements spread across the moon's surface.

"Regardless of the outcome of this final bold experiment, Lunar Prospector has yielded a gold mine of science data," said Henry McDonald, director of NASA's Ames Research Center, which has overseen the mission.

A live web-cast of the event is set for 3 p.m. EDT. Although the crash should have occurred several hours earlier, there may still be a plume of debris visible at 3 p.m.

A vial of astronomer Eugene Shoemaker's ashes will be aboard the spacecraft as it slams into the lunar surface. Shoemaker and his wife discovered about 20 comets and 800 asteroids -- including a comet that collided spectacularly with Jupiter in 1994.

Shoemaker died in a car crash in 1997.

Copyright 1999   The Associated Press. All rights reserved.