This artist's rendering released by NASA shows the Lunar Crater Observation and Sensing Satellite as it crashed into the moon to test for the presence of water last month.
There is water on the Moon, scientists stated unequivocally on Friday.
“Indeed yes, we found water,” Anthony Colaprete, the principal investigator for NASA’s Lunar Crater Observation and Sensing Satellite, said in a news conference. “And we didn’t find just a little bit. We found a significant amount.”
The confirmation of scientists’ suspicions is welcome news to explorers who might set up home on the lunar surface and to scientists who hope that the water, in the form of ice accumulated over billions of years, holds a record of the solar system’s history.
The satellite, known as Lcross (pronounced L-cross), crashed into a crater near the Moon’s south pole a month ago. The 5,600-miles-per-hour impact carved out a hole 60 to 100 feet wide and kicked up at least 26 gallons of water.
“We got more than just a whiff,” Peter H. Schultz, a professor of geological sciences at Brown University and a co-investigator of the mission, said in a telephone interview. “We practically tasted it with the impact.”
For more than a decade, planetary scientists have seen tantalizing hints of water ice at the bottom of these cold craters where the sun never shines. The Lcross mission, intended to look for water, was made up of two pieces — an empty rocket stage to slam into the floor of Cabeus, a crater 60 miles wide and 2 miles deep, and a small spacecraft to measure what was kicked up.
For space enthusiasts who stayed up, or woke up early, to watch the impact on Oct. 9, the event was anticlimactic, even disappointing, as they failed to see the anticipated debris plume. Even some high-powered telescopes on Earth like the Palomar Observatory in California did not see anything.
The National Aeronautics and Space Administration later said that Lcross did indeed photograph a plume but that the live video stream was not properly attuned to pick out the details.
The water findings came through an analysis of the slight shifts in color after the impact, showing telltale signs of water molecules that had absorbed specific wavelengths of light. “We got good fits,” Dr. Colaprete said. “It was a unique fit.”
The scientists also saw colors of ultraviolet light associated with molecules of hydroxyl, consisting of one hydrogen and one oxygen, presumably water molecules that had been broken apart by the impact and then glowed like neon signs.
In addition, there were squiggles in the data that indicated other molecules, possibly carbon dioxide, sulfur dioxide, methane or more complex carbon-based molecules. “All of those are possibilities,” Dr. Colaprete said, “but we really need to do the work to see which ones work best.”
Remaining in perpetual darkness like other craters near the lunar poles, the bottom of Cabeus is a frigid minus 365 degrees Fahrenheit, cold enough that anything at the bottom of such craters never leaves. These craters are “really like the dusty attic of the solar system,” said Michael Wargo, the chief lunar scientist at NASA headquarters.
The Moon was once thought to be dry. Then came hints of ice in the polar craters. In September, scientists reported an unexpected finding that most of the surface, not just the polar regions, might be covered with a thin veneer of water.
The Lcross scientists said it was not clear how all the different readings of water related to one another, if at all.
The deposits in the lunar craters may be as informative about the Moon as ice cores from Earth’s polar regions are about the planet’s past climates. Scientists want to know the source and history of whatever water they find. It could have come from the impacts of comets, for instance, or from within the Moon.
“Now that we know that water is there, thanks to Lcross, we can begin in earnest to go to this next set of questions,” said Gregory T. Delory of the University of California, Berkeley.
Dr. Delory said the findings of Lcross and other spacecraft were “painting a really surprising new picture of the Moon; rather than a dead and unchanging world, it could be in fact a very dynamic and interesting one.”
Lunar ice, if bountiful, not only gives future settlers something to drink, but could also be broken apart into oxygen and hydrogen. Both are valuable as rocket fuel, and the oxygen would also give astronauts air to breathe.
NASA’s current exploration plans call for a return of astronauts to the Moon by 2020, for the first visit since 1972. But a panel appointed in May recently concluded that trimmings of the agency’s budget made that goal impossible. One option presented to the Obama administration was to bypass Moon landings for now and focus on long-duration missions in deep space.
Even though the signs of water were clear and definitive, the Moon is far from wet. The Cabeus soil could still turn out to be drier than that in deserts on Earth. But Dr. Colaprete also said that he expected that the 26 gallons were a lower limit and that it was too early to estimate the concentration of water in the soil.
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