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LCROSS mission concludes but science continues
Posted: October 09, 2009
Updated: October 12, 2009

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The LCROSS mission concluded earlier today with two deliberate impacts into a permanently shadowed crater at the lunar south pole. Scientists will now study the data to determine if water was thrown up in the impacts.

The impacts were separated by just four minutes and were watched by space- and ground-based observatories as the probes met their fate in a crater known as Cabeus.

LCROSS approaches the Moon.

Tony Colaprete, LCROSS principal investigator, reports the mission operated as planned and that the moment of impact was marked with an impact flash as expected. "There was an impact," he confirmed in today's post-impact conference. "We saw the impact. We saw the crater. We got the measurements we need to address the questions of water or no water."

The mission teams reported that the spacecraft performed beautifully throughout the mission, but caution that they need time to comb through the data to ensure they are communicating accurate and correct data. "These are just a first glimpse, we'll learn more and more as the days goes on," says Colaprete.

LRO's Diviner instrument recorded the impact in all four thermal imaging channels. Image: NASA/GSFC/UCLA.

The impact flash of the Centaur impact was observed thermally by the Shepherding Spacecraft from a distance of 6,000 kilometres and filled just one or two pixels – but so far reports of observing the impact debris thrown up by the impact event are uncertain.

"We saw a flash, we saw the crater, so something must have happened in between," says Colaprete, who speculates that perhaps the impact occurred such that debris was ejected more laterally than expected. Once the data has been analysed, the results should reveal information regarding the composition of the material that the probes impacted into – material that may not have seen the light of the Sun for several billion years.

Lining up with crater Cabeus in sight.

Tens of Earth-based telescopes also focused their sights on the Moon, but again, it is too soon to report conclusive evidence of an impact plume, although spectroscopic data reveal distinct differences in before and after measurements. The Hubble Space Telescope was also looking on, and will continue to do so, looking out for any disturbances made to the Moon's exosphere during the impact. Measurements from the orbiting Lunar Reconnaissance Orbiter will also provide a closer look.

"There is a tremendous amount of data," says LCROSS Observation Campaign head Jennifer Heldmann. "We will continue to work together with the LCROSS science team to try and put the pieces together. We're still working on processing but we've collected the data we set out to get, and we're very excited about delving in to start the analysis."

Locations of the Diviner LCROSS impact swaths overlain on a grayscale daytime thermal map of the Moon's south polar region. Image: NASA/GSFC/UCLA.

In just the last few weeks we have begun to look at the Moon in a different light thanks to the confirmation of water on its surface. "We used to think the Moon was a desolate place, now we're seeing a dynamic Moon that's changing on a daily, monthly basis," says Mike Wargo, Chief of lunar science at NASA. "This is NASA at its very best. LCROSS will change the way we look at the Moon scientifically and inform our abilities for continuing to explore the Solar System."

As to whether LCROSS saw water or not, the jury is still out. "The data is only a few hours old," says Colaprete. "I'm excited we saw variations in the spectra which means we saw something happen. The information is there we just need to analyse it and we need a census between spacecraft to confirm the observations and to build up a case for water if it's there or a case against if it's not."

Stay tuned to for further updates as the LCROSS story unfolds.

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