NASA Takes Aim at Moon with Double Sledgehammer Jeremy Hsu
Wed Feb 27, 7:02 AM ET
Scientists are priming two spacecraft to slam into the moon's South
Pole to see if the lunar double whammy reveals hidden water ice.
The Earth-on-moon violence may raise eyebrows, but NASA's history
shows that such missions can yield extremely useful scientific
"I think that people are apprehensive about it because it seems
violent or crude, but it's very economical," said Tony Colaprete, the
principal investigator for the mission at NASA's Ames Research Center
in Moffett Field, Calif.
NASA's previous Lunar Prospector mission detected large amounts of
hydrogen at the moon's poles before crashing itself into a crater at
the lunar South Pole. Now the much larger Lunar Crater and Observation
Sensing Satellite (LCROSS) mission, set for a February 2009 moon
crash, will take aim and discover whether some of that hydrogen is
locked away in the form of frozen water.
LCROSS will piggyback on the Lunar Reconnaissance Orbiter (LRO)
mission for an Oct. 28 launch atop an Atlas 5 rocket equipped with a
Centaur upper stage. While the launch will ferry LRO to the moon in
about four days, LCROSS is in for a three-month journey to reach its
proper moon smashing position. Once within range, the Centaur upper
stage doubles as the main 4,400 pound (2,000 kg) impactor spacecraft
The smaller Shepherding Spacecraft will guide Centaur towards its
target crater, before dropping back to watch - and later fly through -
the plume of moon dust and debris kicked up by Centaur's impact. The
shepherding vehicle is packed with a light photometer, a visible light
camera and four infrared cameras to study the Centaur's lunar plume
before it turns itself into a second impactor and strikes a different
crater about four minutes later.
"This payload delivery represents a new way of doing business for the
center and the agency in general," said Daniel Andrews, LCROSS project
manager at Ames, in a statement. "LCROSS primarily is using
commercial-off-the-shelf instruments on this mission to meet the
mission's accelerated development schedule and cost restraints."
Figuring out the final destinations for the $79 million LCROSS
mission is "like trying to drive to San Francisco and not knowing
where it is on the map," Colaprete said. He and other mission
scientists hope to use observations from LRO and the Japanese Kaguya
(Selene) lunar orbiter to map crater locations before LCROSS dives
"Nobody has ever been to the poles of the moon, and there are very
unique craters - similar to Mercury - where sunlight doesn't reach the
bottom," Colaprete said. Earth-based radar has also helped illuminate
some permanently shadowed craters. By the time LCROSS arrives, it can
zero in on its 19 mile (30 km) wide targets within 328 feet (100
Scientists want the impactor spacecraft to hit smooth, flat areas
away from large rocks, which would ideally allow the impact plume to
rise up out of the crater shadows into sunlight. That in turn lets LRO
and Earth-based telescopes see the results.
"By understanding what's in these craters, we're examining a fossil
record of the early solar system and would occurred at Earth 3 billion
years ago," Colaprete said. LCROSS is currently aiming at target
craters Faustini and Shoemaker, which Colaprete likened to "fantastic
time capsules" at 3 billion and 3.5 billion years old.
LCROSS researchers anticipate a more than a 90 percent chance that
the impactors will find some form of hydrogen at the poles. The
off-chance exists that the impactors will hit a newer crater that
lacks water - yet scientists can learn about the distribution of
hydrogen either way.
"We take [what we learn] to the next step, whether it's rovers or
more impactors," Colaprete said.
This comes as the latest mission to apply brute force to science.
The Deep Impact mission made history in 2005 by sending a probe
crashing into comet Tempel 1. Besides Lunar Prospector's grazing
strike on the moon in 1999, the European Space Agency's Smart-1
satellite dove more recently into the lunar surface in 2006.
LCROSS will take a much more head-on approach than either Lunar
Prospector or Smart-1, slamming into the moon's craters at a steep
angle while traveling with greater mass at 1.6 miles per second (2.5
km/s). The overall energy of the impact will equal 100 times that of
Lunar Prospector and kick up 1,102 tons of debris and dust.
"It's a cost-effective, relatively low-risk way of doing initial
exploration," Colaprete said, comparing the mission's approach to
mountain prospectors who used crude sticks of dynamite to blow up
gully walls and sift for gold. Scientists are discussing similar
missions for exploring asteroids and planets such as Mars.
Nevertheless, Colaprete said they "may want to touch the moon a bit
more softly" after LCROSS has its day.