Findings

by Richard A. Kerr

A near-infrared image of Cabeus crater, taken from Palomar Observatory after the LCROSS impact today. No ejecta are visible from the image, but further analysis may reveal subtle indications of the crash. (Credit: Palomar Observatory/Caltech)

NASA officials and scientists spent the better part of an hour in this morning's press conference patting themselves on the back. The LCROSS mission in search of lunar water was a great success, they said, all the while ignoring a very large elephant in the room: No one among the millions watching as a 2-ton hunk of metal slammed into the moon could see the much-ballyhooed spray of dust and debris that they had been told to look for.

Even LCROSS scientists have seen nothing of a debris plume. "I'm not necessarily surprised," said LCROSS principal investigator Anthony Colaprete of NASA's Ames Research Center in Mountain View, California. In exploration, "you just never know how these things are going to go. We just have to go back with a finer-tooth comb." Colaprete's dogged optimism is grounded in enticing spectroscopic changes detected around the impact site. Determining whether it was water will take weeks or months of data combing.

Actually, Colaprete had warned his colleagues, at least, about the possibility of a no-show debris plume. "It's a very unproven and highly unpredictable science, impact cratering," he told an audience at the Lunar and Planetary Science Conference last March. Impact modelers working for the team had struggled to simulate the impact of a cylindrical--not a simpler spherical--object, and one that was hollow, not solid, like the LCROSS impactor. Plus, it smashed into a surface of unknown shape and composition. LCROSS was "the most challenging impact modeling I've ever done," said Erik Asphaug of the University of California, Santa Cruz, at the time. There were just too many unknowns for him to be entirely comfortable with his results; impact on the odd unseen boulder, for example, could have sent most of the debris into the crater wall instead of into the sky.

LCROSS scientists may yet extract a debris plume from the data, but "the spectra is where the information is" about any water, Colaprete said, referring to spectral colors in the visible, infrared, and even ultraviolet returned by the trailing LCROSS spacecraft and by the Lunar Reconnaissance Orbiter. Some of these showed intriguing blips from the impact flash and the still-warm crater. There were also spectral changes above the impact site between pre- and postimpact. "What do these little blips mean? I don't know," Colaprete said. "I'm just glad they're there. We're going to work on this feverishly." Even so, no public word about water will be forthcoming before the December meeting of the American Geophysical Union, he said.

Start rooting now for the blips.

by Richard A. Kerr

Image of the LCROSS target crater before impact (top), and the last visible-light photo from the spacecraft (bottom). Although intended to produce a visible plume of ejecta, the impact has so far not yielded anything quite so spectacular. (Photos: NASA)

I didn't see anything. Did you? After the 2-ton upper stage of an Atlas rocket slammed into the lunar surface at 7:31 EDT this morning, no one at NASA admitted to spotting the expected spray of dirt and debris rising into the sunlight over the moon's Cabeus crater, as depicted so dramatically in the LCROSS mission overview video. The impactor most certainly plowed into the dark, frigid shadow inside Cabeus as planned, and the nine instruments on the trailing LCROSS spacecraft returned all the planned data. But no flash was reported at the moment of impact, and no debris could be seen. The science team's only report was "confirm crater in mid IR [infrared]," an apparent sighting of the impactor's hole in the ground. LCROSS itself then hit the moon, with mission control reporting a "loss of signal."

If the rocket impact failed to throw sufficient debris out of the lunar shadows to be detectable, it would not come as a complete surprise. Calculating just how the impact would excavate a crater in the lunar soil and rock "was the most challenging impact modeling I've ever done," Erik Asphaug of the University of California, Santa Cruz, said last spring. If high-rising ejecta were a no-show, there will be little chance of detecting minerals that could have been hydrated by subsurface ice. On the bright side, any water that turned to vapor would have expanded well beyond any solid ejecta and surely have risen into the sun, where some of LCROSS's instruments could have seen it. One can hope.

For those of you who want to follow the event blow-by-blow as NASA sends a rocket crashing into the moon on Friday, 9 October:

• 6:15 a.m. EDT  NASA TV begins a live broadcast of the mission. Watch here.
• 7:31 a.m. EDT  Lunar impact!
• 10:00 a.m. EDT  NASA postimpact news conference.
• 12:00 p.m. EDT  Science's resident space expert Richard Kerr will blog his preliminary analysis of the mission's findings.
• 3:00 p.m. EDT  Richard Kerr will blog a full wrap-up and analysis of the LCROSS mission.
• 4:00 p.m. EDT  Live Facebook chat with Richard Kerr. Submit your questions now, and follow the chat here.

We will also be covering the event on Twitter.

Don't expect this one to win any MTV music video awards, but the LCROSS mission has its own theme song. NASA credits the tune to LCROSS Deputy Project Manager John Marmie and his friend Jeff Petro. Check out the video below. It's sure to become a staple of late-night NASA TV.

by Richard A. Kerr

Hang on, NASA's about to blast for lunar gold. Tomorrow at 7:30 a.m. EDT, an Atlas rocket's 2-ton spent upper stage will slam into the frigid, eternally dark floor of Cabeus crater near the moon's south pole. The target? Water ice trapped for eons beneath the surface that could slake the thirst of lunar astronauts and even fuel a trek to Mars--assuming the water's really there, of course.

Theory allows for water ice in such lunar cold spots, and remote sensing has hinted at it, but no one knows what tomorrow's impact will throw into the lunar sky. All the world will be watching to find out. The LCROSS spacecraft will be trailing 4 minutes behind the impactor, sending its close-up view back to Earth to be streamed live by NASA. Astronomers on the ground will have their biggest scopes trained on the impact. And then the trailing LCROSS craft will fly through the ejecta cloud and augur in. If the sensors arrayed for the occasion shout "Water!," we'll hear about it at a 10:00 a.m. EDT NASA press conference. If not, it'll be a busy holiday weekend for LCROSS scientists.

Here is a video overview of the mission from NASA:

After you finish "waltzing" through that video, also be sure to check out this higher resolution animation of the spacecraft, the last half of which contains a video of the launch.

Still want more? I'll be answering reader questions about the LCROSS mission and lunar exploration on ScienceNOW's Facebook page. You can post your questions there now, or join me for a live discussion tomorrow from 4-5 p.m. EDT.

NASA has an LCROSS project page with videos, pictures, and a live telecast. NASA's Ames Research Center also has an LCROSS mission page with a few videos and some news.