for National Geographic News
LCROSS (Lunar Crater Observation and Sensing Satellite) and its rocket will begin slamming into the South Pole just after 4:30 a.m. PT.
The LCROSS collision should reveal how much water ice exists in the permanently shadowed craters of the moon. Some theories suggest the lunar pits hold vast stores of water.
How to Watch LCROSS Moon Crashes
Unlike most cosmic impacts, though, the LCROSS crashes will have an audience: Many amateur astronomers in the Americas will have their telescopes trained on the impact site. Even more can watch the LCROSS moon impact on the NASA TV Web site.
Enthusiasts on the U.S. East Coast should tune in, since their view of the LCROSS impact will be blocked by early morning sunlight, experts say.
Only North, Central, and South America will be facing the moon at the time of the LCROSS impact, allowing astronomers and stargazers there a rare view, experts say.
Anyone in these regions with at least a 10-inch (25.4-centimeter) telescope should be able to catch a glimpse of dusty debris—and maybe water vapor—billowing into the sunlight above the crater's rim, astronomers say.
"If you have a telescope trained in the right location, you should be able to see the plume come up and have some brightening over a short amount of time," said Jennifer Heldmann, the LCROSS observation campaign coordinator at NASA Ames Research Center in Moffett Field, California.
"And then you'll see that, as the plume settles back down onto the lunar surface, it will become fainter and more diffuse, and then it will disappear again."
LCROSS to Find Moon Water?
Last month a suite of studies in the journal Science concluded that the moon is saturated with at least hydrogen and oxygen, the ingredients of water—ending years of speculation.
If abundant lunar water ice is found, it could someday be used to slake the thirst of moon colonizers and fuel their journeys deeper into space. (Read more about moon exploration.)
The water ice search will begin when the LCROSS satellite releases its spent launch rocket, Centaur, toward the moon. When the rocket hits, it should kick up dusty debris from the crater floor into the light of day.
LCROSS will pass through the plume about four minutes after Centaur's crash, measuring the debris with nine instruments and relaying data back to mission control.
Then the satellite itself will crash into the moon, Heldmann said.
The debris plumes will last no more than two minutes—billowing 1.2 to 22 miles (2 to 35 kilometers) above the crater rim—before they start to fade, NASA says.
The Centaur rocket weighs about 4,850 pounds (2200 kilograms)—roughly the size of a sport utility vehicle. The satellite is about a third that size.
LCROSS a Smash Hit for Astronomers
Though similar-size objects hit the moon several times per month, the LCROSS impact gives astronomers a rare opportunity to plan for a collision, Heldmann said.
"It is not everyday that NASA smashes stuff into the moon," said amateur astronomer Jerry Hilburn of the San Diego Astronomy Association in California.
Up to 300 people will view the crash at the association's Tierra Del Sol observatory compound in the mountains east of San Diego.
The association is among dozens of groups organizing "star parties" to watch the event.
The astronomy association will submit the images they make to the LCROSS Citizen Science Web site, which will help the space agency study the impact from a variety of viewpoints.
"This is a really good way for amateurs to become actively involved in this mission," Heldmann said.
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