Is there water on the Moon? Startling discovery could change lunar exploration forever
Moon could harbor roughly 15,000 square miles of permanent shadows in multiple shapes and sizes, reservoirs that, according to theory, may also be capable of preserving water via ice
For years, scientists have been trying to uncover the mysteries of water on the Moon. While previous studies have suggested that there is water on the Moon, new findings conclude that those hold water. Researchers have confirmed, for the first time, water on the sunlit surface of the Moon. This discovery indicates that water may be distributed across the lunar surface, and not limited to cold, shadowed places. Water on the Moon may also be more abundant than previously thought, suggests another analysis. These findings could have massive implications for future Moon missions, which would want to take advantage of the resources on the lunar surface. This includes NASA’s Artemis program that aims to return humans to the Moon by 2024, and eventually create a permanent base at the lunar South Pole called the Artemis Base Camp.
NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) detected water molecules (H2O) in Clavius Crater, one of the largest craters visible from Earth, located in the Moon’s southern hemisphere. Previous observations of the Moon’s surface detected some form of hydrogen but were unable to distinguish between water and its close chemical relative, hydroxyl (OH). Data from this location reveal water in concentrations of 100 to 412 parts per million — roughly equivalent to a 12-ounce bottle of water — trapped in a cubic meter of soil spread across the lunar surface. As a comparison, the Sahara desert has 100 times the amount of water than what SOFIA detected in the lunar soil, explains NASA. According to experts, despite the small amounts, the finding raises questions about how the water was created and how it exists on the harsh, airless lunar surface.
“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,” says Paul Hertz, director of the Astrophysics Division in the Science Mission Directorate at NASA Headquarters in Washington. The study has been published in Nature Astronomy.
Understanding how much water is on the Moon will allow future missions to bring more equipment for science. “Water is a valuable resource, for both scientific purposes and for use by our explorers. If we can use the resources at the Moon, then we can carry less water and more equipment to help enable new scientific discoveries,” explains Jacob Bleacher, chief exploration scientist for NASA’s Human Exploration and Operations Mission Directorate.
When the Apollo astronauts first returned from the Moon in 1969, it was thought to be completely dry. Whether the water SOFIA found is easily accessible for use as a resource remains to be determined. Under NASA’s Artemis program, scientists hope to learn more about the presence of water on the Moon before sending the first woman and next man to the lunar surface in 2024 and establishing a sustainable human presence there by the end of the decade.
The telescope that made it possible
Flying at altitudes of up to 45,000 feet, SOFIA, the modified Boeing 747SP jetliner with a 106-inch diameter telescope can reach above 99% of the water vapor in Earth’s atmosphere to get a clearer view of the infrared universe. Using its faint object infrared camera for the SOFIA Telescope (FORCAST), it was able to pick up the specific wavelength unique to water molecules, at 6.1 microns, and discovered a “relatively surprising concentration” in sunny Clavius Crater.
Many forces could be at play in the delivery or creation of this water, suggest experts. The water may be delivered by micrometeorites that land on the lunar surface and carry small amounts of water. Another possibility could be that the Sun’s solar wind delivers hydrogen to the lunar surface and causes a chemical reaction with oxygen-bearing minerals in the soil to create hydroxyl. Meanwhile, radiation from the bombardment of micrometeorites could be transforming that hydroxyl into water.
SOFIA’s follow-up flights will look for water in additional sunlit locations and during different lunar phases to learn more about how the water is produced, stored, and moved across the Moon. The data will add to the work of future Moon missions, such as NASA’s Volatiles Investigating Polar Exploration Rover (VIPER), to create the first water resource maps of the Moon for future human space exploration.
“Prior to the SOFIA observations, we knew there was some kind of hydration. But we didn’t know how much, if any, was actually water molecules — like we drink every day — or something more like drain cleaner,” says Casey Honniball, the lead author who published the results from her graduate thesis work at the University of Hawaii at Mānoa in Honolulu.
Water could be trapped in small shadows
Hidden pockets of water could be much more common on the surface of the Moon than scientists once suspected, according to a separate study led by CU Boulder. The team used theoretical models and NASA's Lunar Reconnaissance Orbiter data to suggest that water could be trapped in small shadows, where temperatures stay below freezing, across more of the Moon than currently expected. In some cases, these tiny patches of ice might exist in permanent shadows no bigger than a penny, explain authors.
“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,” writes Paul Hayne, assistant professor in the Laboratory of Atmospheric and Space Physics at University of Colorado Boulder, in the study, which has also been published in Nature Astronomy.
The research team explored phenomena on the Moon called “cold traps” — shadowy regions of the surface that exist in a state of eternal darkness. Many have gone without a single ray of sunlight for potentially billions of years, and these nooks and crannies may be a lot more numerous than previous data suggest. The investigations estimate that the Moon could harbor roughly 15,000 square miles of permanent shadows in multiple shapes and sizes — “reservoirs that, according to theory, might also be capable of preserving water via ice.” Previous estimates pegged the area of cold traps on the Moon at around 7,000 square miles, about half of what the current analysis has predicted.
The team notes that they cannot actually prove that these shadows hold pockets of ice — the only way to do that would be to go there in person or with rovers and dig. However, the results are promising, and future missions could shed even more light on the Moon’s water resources, they emphasize. “If we’re right, water is going to be more accessible for drinking water, for rocket fuel, everything that NASA needs water for,” suggests Hayne.
Hayne himself is leading a NASA effort called the Lunar Compact Infrared Imaging System (L-CIRiS) that will take heat-sensing panoramic images of the Moon’s surface near its south pole in 2022. “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,” he says.