Declaring "This is not your father's moon," National Aeronautics and Space Administration scientists said Friday that last month's mission to punch a hole in the lunar surface found significant amounts of water in a permanently shadowed crater at the moon's south pole.
"The moon is alive," declared Anthony Colaprete, the chief scientist for the Lunar Crater Observation and Sensing Satellite mission.
According to Colaprete and other researchers, the mission measured about 25 gallons of water in the form of vapor and ice after punching a hole about 100 feet across in the surface of the moon. Although that's not enough to bathe in, it could be evidence there is enough water at the poles for future astronauts to use to live off the land. And it's far more than anyone expected following the Apollo missions of the 1960s and '70s, which pronounced the moon a dead, forbidding world.
"This is painting a surprising new picture of the moon," said Greg Delory, a space scientist at the University of California, Berkeley.
The $79 million lunar crater mission was launched in June to try to uncover the source of large quantities of hydrogen that had been measured by other spacecraft in lunar craters at the poles. If there was water on the moon, scientists reasoned, it would be in these shadowed craters, which haven't seen sunlight in billions of years.
Because those craters were hidden from view, scientists decided the best way to find out what was in them was to go there. Early on the morning of Oct. 9, the lunar crater satellite targeted the Cabeus crater at the South Pole, first steering its companion Centaur rocket into the crater. The satellite then flew through the cloud of debris and dust kicked up by the Centaur, using its near-infrared and visible light spectrometers, along with other instruments, to taste the contents of the debris cloud. Spectrometers identify compounds by analyzing the light they emit or absorb.
No cloud showed up at first, causing some scientists to worry that the Centaur had hit rock. But the scientific team became excited when they started looking at the data transmitted back to Earth just before the satellite itself crashed a short distance from the Centaur.
The eureka moment came in recent weeks when the team realized a strong signature for water was picked up in more than one instrument.
"What's really exciting is we've only hit one spot," said Peter Schultz, a geology professor at Brown University and a co-investigator on the mission. "It's kind of like when you're drilling for oil. Once you find it in one place, there's a greater chance you'll find more nearby."
This is not the first discovery of water on the moon. Several weeks ago, India's Chandrayan spacecraft found clear signs of a microscopic film of water mixed in with lunar soils, or regolith, over large areas of the moon. But those amounts were so insignificant that it is unlikely that that water would be of use to future colonists. This latest discovery, however, is a potentially significant source of water, the scientists said.
The question now is, where did it come from? Possible sources include comets and asteroids. It's also possible the hydrogen was delivered by solar wind to the lunar surface, where it is converted to water and travels to the shadowed craters. There, the water could be stored in the form of ice for billions of years. Polar craters on the moon are some of the coldest places in the solar system, with temperatures dipping lower than minus 360 degrees Fahrenheit.
The scientists hinted that other surprises may be coming in the next few months, as they continue studying the data from the mission, dubbed the LCROSS. "The full understanding of the LCROSS data may take some time. The data is that rich," Colaprete said.