NASA's LCROSS spacecraft and its booster rocket are on course to crash into the moon's south pole Friday morning as scientists make another bid to determine whether there is useful water ice hidden in the rocks and soil of a deep polar crater.

The idea is to blast enough of the moon into space with the booster's impact that detectors on board LCROSS itself can measure the water in the debris and send the data back to Earth before the spacecraft itself follows its booster into the dirt. (No, it won't hurt the moon.)

Plans call for both objects to target the Cabeus crater, impacting at 7:31 a.m. and 7:35 a.m. EDT. Scientists and engineers at the Goddard Space Flight Center are playing roles in the the mission's final moments.

Both impacts will also be watched closely through telescopes on Earth and in orbit, in the expectation that one or both crashes will reveal the presence of water. If the answer is positive, it would be a boost to hopes that a manned base at the south pole would have access to water, for drinking and for hydrolysis, which breaks the H2O into hydrogen and oxygen.

The oxygen could help supply the base with breathable air, and the two gases - if there's really enough there - could be repackaged and used as fuel for sending rockets and people back to Earth, or elsewhere in the solar system.

Previous unmanned missions to the moon have provided hints of hydrogen at the poles. And the Lunar Reconnaissance Orbiter mission now circling the moon has detected a thin, volatile "dew" of water on the lunar surface.

But lunar mission planners are especially interested in water ice at the polar craters. The moon's poles are attractive to base-builders because high elevations could provide nearly constant sunlight for solar electric generation, and shelter (thanks to the steady, low sun angles) from the extremes of heat and cold that prevail closer to the moon's equator.

And the deep polar craters, thanks to the absence of sunlight, are where scientists suspect water ice - delivered during the early bombardment of the inner solar system by icy comets - is most likely to have been preserved.

Unfortunately for people in Maryland, and anywhere east of the Mississippi, the LCROSS impacts won't be visible directly because the moon will have set. (SEE COMMENTS BELOW) In any case, you would need a telescope, with a lens or mirror at least 10 inches in diameter. But there will be ways to watch the events in your jammies via Webcast. Here are some of them:

NASA TV will Web cast the impacts beginning at 6:15 a.m. EDT. There is an onboard camera that should send back dizzying video of the fall.

LCROSS has a Twitter site, too. Follow developments minute to minute.

The mission is also on Facebook, believe it or not. Looks pretty nasty to me, but I guess you could be a friend for a few hours.

Also, the online SLOOH telescope system will provide live Web feeds of the impact.