That's the stage that scientists find themselves in after what they say was a successful mission aimed at seeing whether deep, frigid polar craters hold a precious resource – something that future moon explorers could use to help keep themselves alive.
By everyday standards, the crash of two craft at the bottom of Cabeus crater at the moon's south pole was a visual dud, even by the low expectations that researchers had set in advance. At least one observatory initially indicated it failed to pick up a visible plume of material, which the collisions should have kicked up.
"We don't see a plume clearly in the images yet," acknowledged Anthony Colaprete, the mission's lead scientist, during a post-impact press briefing.
Some form of plumes may emerge as the images are more carefully processed, he said.
But in the end, the clues that scientists crave come from LCROSS's spectrometers. They look for the telltale fingerprints of chemicals and molecules in light.
These instruments generate graphs with the “squiggly lines scientists love," says Jennifer Heldmann, a member of the research team coordinating the overall observation effort. They should help answer the mission's fundamental question regarding the presence – or absence – of water ice.
"We got the data we needed to address the question," says Dr. Colaprete, with the National Aeronautics and Space Administration's Ames Research Center at Moffett Field, Calif.
The first craft, a bus-sized spent upper stage from the rocket that launched LCROSS and its sister mission the Lunar Reconnaissance Orbiter, hit at about 7:32 EDT Friday morning. Roughly four minutes later, it was followed by the LCROSS craft itself – a package of cameras and spectrometers that also guided the duo to become artificial meteors. The two separated Thursday evening, allowing the LCROSS package to fly through and measure the traits of any plume that the upper stage kicked up.
During LCROSS's final approach, it picked up the flash of the upper stage's impact and registered the heat signature from the crater that the crash generated.
Indeed, these are initial bright spots in the first look at the data. The flash contained a strong signature of the element sodium. Researchers don't yet have an explanation, although sodium is a minor ingredient in the moon’s tenuous atmosphere.
In addition, LCROSS spectrometers picked up a strong indication that the first impactor triggered significant changes to the lunar atmosphere above the site. Now, scientists have to figure out what those changes were and whether water vapor, or any of water's constituents, was present.
The presence of ice certainly would represent a eureka moment. The possibility has tantalized lunar scientists and advocates of human lunar exploration since the Lunar Prospector mission in 1999 returned indirect evidence for water ice in polar craters. Its instruments recorded strong signals indicating hydrogen was present. But there's nothing like the direct detection of water molecules to make the most convincing case.
If it turns out that LCROSS did not turn up water, it could mean that water isn’t there, says Michael Bicay, science director at Ames. But, he adds, he doubts this is the case because the hydrogen signals detected by other missions have been so consistent and strong.
It also could be that water ice is less abundant than theorized, so LCROSS's instruments couldn't pick it up. That would imply too little water for explorers to use.
Or, "like old Texas wildcatters, we may have hit a dry hole," Dr. Bicay says, meaning that ice isn't evenly distributed.
A microwave for lunar research?
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