For years, scientists have known that water and ice exist on the moon in some form, likely at its poles in deep, dark craters. But these craters are some of the coldest places in the solar system, making exploration tricky. Now, two new studies published yesterday in the journal Nature Astronomy confirm that water can be found all over the moon's surface in varying states, which could make extracting this valuable resource on future missions much easier.
In one study, scientists found evidence that water molecules can be found in subtle, trace amounts in the moon's sunlit areas nearly 100 times drier than the Sahara Desert, reports Ashley Strickland for CNN. Another team of researchers estimate that ice kept cool by permanent shadows at the poles might be 20 percent more abundant than previously thought, and it may be accessible outside of hard-to-reach craters, reports Maya Wei-Haas for National Geographic.
In 2009, researchers detected faint traces of water on moon's surface using instruments on board spacecrafts. But the tool they were using couldn't detect the difference between water and hydroxyl, a molecule that consists of one hydrogen atom and one oxygen atom.
To get a more accurate estimate, NASA deployed a jumbo jet carrying a nine-foot, 17-ton telescope called SOFIA, or the Stratospheric Observatory for Infrared Astronomy. SOFIA can harness part of the infrared spectrum that can only detect H2O.
Using data collected by SOFIA, researchers found that roughly 12 ounces of water are locked in a cubic meter of dirt, lead author Casey Honniball of NASA’s Goddard Spaceflight Center tells National Geographic. The water is trapped among the shadowed patches of lunar soil or in glassy materials left behind by micrometeorite impacts, reports Sid Perkins for Science.
“To be clear, it’s not puddles of water, but instead water molecules that are so spread apart that they do not form ice or liquid water,” Honniball tells Kenneth Chang for the New York Times.
But how the water persists in these sunny spots is still unclear, since scientists would have expected the sun's rays to bounce the molecules back into space.
While this study detected water in the dry lunar soil, a separate study focused on the icy spots hidden in the shadows of the moon's craters. Temperatures in the craters can drop to around negative 400 degrees Fahrenheit and trekking into a region so dark, deep and cold would be too dangerous for exploration, the Times reports.
A team of researchers led by Paul Hayne, a planetary scientist at the University of Colorado, Boulder, examined high-resolution images of the moon's surface and found that these icy patches cover an estimated 15,400 square miles, which is roughly the size of Maryland and Delaware combined. Around 60 percent of those frozen patches are in the moon's southern hemisphere, possibly in areas outside of craters that are safe enough for astronauts to explore.
The team modeled shadows and temperatures on the moon and discovered that ice can form in the tiny patches—some as small as an ant, reports National Geographic. These bits can be just as cold as the moon's deep craters, but they're smaller and shallower. If all these zones, dubbed "micro cold traps," are filled with ice and frost, they could amount to trillions of pounds of water, Hayne tells National Geographic. The depressions could be cold enough have stored the water for millions or billions of years, which could help "us understand the origins of earth's water," he tells the Times.
As NASA prepares for Artemis—a mission to return humans to the moon by 2024—and gears up for a highly anticipated expedition to Mars in the 2030s, the agency says it is eager to "learn all it can about the presence of water on the moon." In the meantime, researchers will be figuring out how to best "mine" the moon's water in hopes of someday using it on future space voyages.
The discoveries are a "real game changer" for future astronauts and rover missions, lead author Paul O. Hayne, a planetary scientist at the University of Colorado, Boulder, tells the Times. Hopefully, some of the water can be transformed into potable drinking water, of course, but astronauts can make full use of the material by breaking apart H2O atoms. By separating the elements, astronauts could capture oxygen to breathe, and the hydrogen and oxygen atoms can both be used as rocket propellants. Being able to launch rockets from the moon could make it an excellent pitstop on the way to Mars or for a journey back to Earth.
“Water is a valuable resource, for both scientific purposes and for use by our explorers,” Jacob Bleacher, a chief exploration scientist at NASA, says in a press release. “If we can use the resources at the moon, then we can carry less water and more equipment to help enable new scientific discoveries.”