Early Friday, a spacecraft is scheduled to punch a hole in a crater near the moon's south pole that hasn't seen sunlight in billions of years. The purpose: to find out whether ice is hidden there.
NASA's Lunar Crater Observation and Sensing Satellite, which set out for the moon in June, made a late course correction Tuesday to position itself to steer a rocket into the 2-mile-deep crater Cabeus at 7:30 a.m. Friday.
Four minutes later, if all goes according to plan, the spacecraft will fly through the cloud of debris that will rise above the lunar surface and linger there for less than a minute. As it passes through the cloud, the satellite's nine instruments will analyze the dust and debris for evidence of water, before crashing itself.
Scientists preparing for the collision could hardly contain their excitement over what might turn up.
"It's our job to confirm there is water there," said Dan Andrews, the project manager at Ames Research Center in Mountain View, Calif., which designed the spacecraft's instruments. "But even if it's very dry, that's a good answer to have."
The LCROSS satellite was originally a $79 million add-on to the larger, $500 million Lunar Reconnaissance Orbiter, whose mission is to map the moon. But the theatrical nature of the impact event has caught the attention of the public.
Thousands of people are expected to show up tonight at the Ames complex south of San Francisco for music and movies, culminating with a live video feed of the impact.
NASA says the rocket will be traveling about 5,600-miles-an-hour when it plunges into Cabeus. That will create a dust cloud rising as much as 6 miles above the lunar surface, providing a rare show for amateur astronomers.
The collision can theoretically be seen throughout the southwest and as far away as Hawaii, providing the observer has a large enough telescope at hand and good viewing conditions.