for National Geographic News
But LCROSS impact and similar crashes have some experts are urging extra caution for the future.
LCROSS (Lunar Crater Observation and Sensing Satellite) gouged what was expected to be a 100-foot-wide (30-meter-wide) hole in a shadowy crater near the moon's south pole, letting fly more than 200 tons of material, scientists estimated before the launch.
Such violent impacts are par for the course—the moon is already littered with more than two dozen NASA landers, orbiters, and rovers launched since the 1960s.
But as the new international space race heats up, there's a growing movement to balance scientific ambition with its possible consequences for the moon.
"Any time you crash, obviously you destroy some area of lunar surface for any kind of scientific study, and that's not good," said NASA's lunar sample curator Gary Lofgren, speaking with National Geographic News earlier this year. (Read about NASA's moon-rock collection.)
Last year the International Council for Science's committee on space research imposed new documentation requirements to maintain the integrity of future discoveries—and LCROSS-like crashes—on the moon.
"You want to be able to understand what materials you brought with you versus what materials would have been deposited there naturally," said Catharine Conley, NASA's planetary-protection officer.
LCROSS Impact: Merely a Flesh Wound?
SUV-size LCROSS and its used-up, two-ton Centaur rocket both crashed into the moon today.
The world's telescopes were watching for the LCROSS impact's kicked-up debris, and amateur astronomers were expected to be able to see the dust cloud, however faint, with good backyard telescopes.
NASA officials say the LCROSS mission is key to the future of moon exploration. If the probe confirms reservoirs of ice on the moon, those water sources could support bases that might eventually propel humans to Mars and beyond.
As for litter, most of the LCROSS probe will be vaporized on impact, said NASA spokesperson Grey Hautaluoma, and the craft's fuel will be vented prior to impact to avoid contaminating data on the debris cloud.
(Read more about moon exploration.)
LCROSS Moon Crash Worth the Price
According to lunar-sample curator Lofgren, any damages inflicted by crashes on the moon so far have been a small price to pay for decades of lunar science.
Currently spacecraft remains occupy only a small portion of the moon's surface, he said.
What's more, meteors usually crash at about 15 miles (25 kilometers) a second, wreaking havoc on the moon's surface. For the most part, human-caused moon impacts hit at a tenth of that speed.
Spacecraft impact just "throw stuff around," he said. "It's not vaporizing materials. It's not melting rocks."
And because the moon has no atmosphere and no wind, the debris doesn't move around and contaminate other places, he said.
"They're just pieces of metal sitting on the surface."
Planetary protection officer Conley noted that contamination protections for the barren moon—where no known life could survive—will never be as stringent as they are for potentially habitable places like Mars.
NASA's Mars-bound spacecraft are meticulously sterilized, and plans are already being developed for the medical-grade quarantine that will await any Martian samples that could one day return to Earth.
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