An Atlas V rocket is on a collision course with the moon, and when it hits early Friday morning, the blast will kick up a miles-high plume of debris visible from Earth. Or at least that's what NASA scientists are hoping.

Their goal is to find water -- if there is any to be found -- frozen deep in the permanently shaded floor of a crater at the moon's south pole. Water will be key to the success of future moon colonies, and not just for drinking; it can be split into oxygen for breathing and hydrogen for fuel.

Viewing parties

Viewing parties are planned up and down the coast. Here are details on three local gatherings, all free:

Portland:

OMSI, at 1945 SE Water Avenue in Portland, will project the impact in its auditorium via a live satellite feed from NASA starting at 3:30 a.m. More info: 800.955.6674 or

Sun River:

The Sun River Nature Center and Observatory, located next to Lake Aspen on River Road, will have 10 telescopes for eye-witness viewing, and play live satellite feed from NASA on video screens, starting at 4 a.m. More info: 541-593-4442

Ellensburg, Wash.:

Central Washington University's astronomy club will have three telescopes, including a 12-inch scope with a CCD camera to photograph the impact, and play live satellite feed from NASA, starting at 3:30 a.m. at Lind Hall (Northwest corner of University Way/8th Ave. and Chestnut St.) More info: email:

, Web:

"With that you have the basics for human sustainability," says John Marmie, deputy project manager for NASA's Lunar Crater Observing and Sensing Satellite, or

.

The show starts at 4:31 a.m. Friday, when the spent upper-stage of the Atlas V rocket strikes its target: an ancient crater called Cabeus that's 60 miles across and nearly a mile deep. Four minutes later, a second spacecraft will fly through the debris plume, collecting and relaying observations back to Earth before smashing into the moon and lofting a second debris plume.

Oregon and the rest of the West coast will have good views for amateur astronomers using telescopes with a diameter of at least 10 inches, say NASA scientists, who've posted

. The impacts won't be big enough to see with the naked eye or binoculars.

But the drama will play out under scrutiny by 18 major earth-based observatories and four earth-orbiting instruments, including the Hubble space telescope, Marmie says.

Previous moon orbiters have found likely signs of water. Last month, for instance, a NASA instrument on the Indian Space Research Organization's Chandrayaan-1 spacecraft measured wavelengths of light absorbed on the lunar surface that matched the pattern expected of water molecules. But the concentration appears small: about 32 ounces per ton of moon dust, researchers estimate.

LCROSS scientists hope their $79 million experiment provides definitive evidence of water, and a clearer picture of how much might exist at the moon's south pole. But some scientists say the mission faces big uncertainties.

For one thing, the hollow rocket stage may not produce a big enough bang. Peter Schultz of Brown University told Science magazine that NASA's models may underestimate the chances that debris will hit the crater rim instead of rising into view. In experiments with hollow projectiles fired into fake lunar soil, Schultz found that blasts spread at lower angles than with solid projectiles. Schultz said the dirt and rubble of the upper few meters of the moon is highly compressible and challenging to predict how it will absorb impact.

NASA scientists are more confident. "Our simulations show that the debris will get kicked up long enough for us to view it," Marmie says. "We think it's gonna work."

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