Scientists have wondered for years if water is present on the moon. Just over a decade ago, new spacecraft identified chemical signatures of water on our nearest solar neighbor. However, scientists at the time hypothesized that it was hydroxyl, a compound that’s one hydrogen atom away from being the water we know and love.
Now, NASA has used a flying infrared telescope to determine that true H2O is present on the moon’s surface. Although much of it is trapped in glass beads, regolith, or is hiding in deep shadows, it is there. A duo of studies, both published in the journal Nature Astronomy, detailed the findings.
Gazing in Infrared
The first study utilized data from NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) airborne telescope. In essence, SOFIA is a 2.7-meter long telescope mounted to a Boeing 747. The plane is flown at 43,000 feet, which is above most of the water in the Earth’s atmosphere.
Jessica Sunshine, an astronomer from the University of Maryland, says, “Between us and the moon is a lot of water.”
That H2O can make infrared observations difficult. Flying the telescope above the water vapor gives it a clearer picture of the moon. “I’m surprised nobody thought to do it sooner,” says Sunshine.
Thanks to those new observations, NASA was able to confirm the presence of true water on the moon. The agency’s director of astrophysics for the Science Mission Directorate, Paul Hertz, said in a press conference on Monday, “We had indications that H2O—the familiar water we know—might be present on the sunlit side of the moon. Now we know it is there. This discovery challenges our understanding of the lunar surface and raises intriguing questions about resources relevant for deep space exploration.”
Much of the water found during the SOFIA observations is located around the Clavius Crater on the southern portion of the moon. NASA says that there is roughly the equivalent of a 12-ounce bottle of water trapped in grains of the lunar surface. This protects it from the harsh external environment.
Of course, the question of how water got to the moon’s surface remains. Lead study author Casey Honniball is wondering this very thing. He says, “Without a thick atmosphere, water on the sunlit lunar surface should just be lost to space. Yet somehow we’re seeing it. Something is generating the water, and something must be trapping it there.”
Current theories suggest that the water is delivered via micrometeorites that strike the lunar surface while carrying trace amounts of water. Another possibility is that solar wind delivers the hydrogen ions necessary to cause a chemical reaction with oxygen in the moon’s soil to create hydroxyl. When hit by a meteorite, that hydroxyl could become water.
Even More Water
Although water on the sunlit portion of the moon remains more of a mystery, water in the shadows is easier to explain. After all, near the moon’s poles, dense shadows provide respite from harsh solar radiation and heat.
The second study announced on Monday used data from the Lunar Reconnaissance Orbiter to study areas called cold traps that lurk within these shadows. Researchers found that most of the ice near the poles isn’t hidden in large pools but rather in small, penny-sized patches.
Paul Hayne, lead study author and assistant professor at the University of Colorado Boulder, says, “If you can imagine standing on the surface of the moon near one of its poles, you would see shadows all over the place. Many of those tiny shadows could be full of ice.”
Although tiny patches don’t sound like much, they quickly add up. Researchers estimate that the moon’s shadowy areas could contain an abundance of these “micro” cold traps. The team concluded that there could be as much as 15,000 square miles capable of preserving water in the form of ice. That dwarfs previous estimates which suggested 7,000 square miles of such area.
Hayne says, “If we’re right, water is going to be more accessible for drinking water, rocket fuel, everything that NASA needs water for.”
That being said, the ice isn’t easy to get to. At the extremely cold temperatures in the moon’s shadows, ice behaves like a rock, according to Hayne. Astronauts and lunar rovers will need to manually dig it out before it can be used. That process will be both taxing and time-consuming.
What Does it Mean for Artemis?
NASA’s near future is tied closely to the moon. The agency plans to land human astronauts there by 2024. Until then, we’ll have to rely on infrared data to confirm the presence of ice. Once astronauts arrive, things could look a lot different.
“Astronauts may not need to go into these deep, dark shadows. They could walk around and find one that’s a meter wide and that might be just as likely to harbor ice,” Hayne says.
With hopes of establishing a permanent base on the moon, NASA would be happy to find that water is plentiful enough to harvest. After all, transporting water from Earth is extremely expensive. However, it is necessary not only for the survival of astronauts but also plays a role in many scientific experiments.
Jacob Bleacher, chief exploration scientist in NASA’s advanced exploration systems division, says, “Water is a valuable resource, for both scientific purposes and for use by our explorers. If we can use the resources on the moon, then we can carry less water and more equipment to help enable new scientific discoveries.”
One thing is certain. Artemis astronauts will be bringing their own supply of water along for the ride. Until we can confirm the presence of water on the moon in person, it is too risky to count on it.