There may be more water on the moon than previously believed, and it could be used as a resource during upcoming missions -- like NASA's return of humans to the lunar surface through the Artemis program.
The two studies published in the journal Nature Astronomy, and researchers shared their findings during a NASA press conference on Monday.
The research is based on data gathered by NASA's Lunar Reconnaissance Orbiter, in orbit around the moon since June 2009, as well as the agency's Stratospheric Observatory for Infrared Astronomy airborne telescope, called SOFIA. The latter is a Boeing 747SP aircraft modified to carry a 2.7-meter telescope.
In the first study, researchers used SOFIA to observe the moon at a wavelength that revealed the signature of molecular water, or H2O.
"For the first time, water has been confirmed to be present on the sunlit surface of the moon," said Paul Hertz, NASA's Astrophysics Division director during Monday's press conference.
Previous research revealed detections of water on the surface of the moon near the south pole. But the signature of molecular water at the wavelength used in this research could also be associated with hydroxyl, which is oxygen bonded with hydrogen. In organic chemistry, alcohols tend to include hydroxyl, which contributes to making molecules soluble in water. Hydroxyl is also an ingredient in drain cleaner.
The SOFIA detections confirm that water, not hydroxyl, can be found trapped in glass beads or in between grains on the moon at its high southern latitudes. There, water is present between 100 to 400 parts per million.
The fact that this water is inside grains or in between grains on the lunar surface helps protect it from the moon's harsh and irradiated environment.
In the second study, researchers used data from the lunar orbiter to study cold traps in permanently shadowed areas on the moon where water could remain frozen. Some of these cold traps may have evaded the sun for billions of years.
ICE-FILLED POLAR TRAPS
The most common hidden pockets of water across the lunar surface could be trapped in tiny penny-size ice patches that live in permanent shadows, the researchers discovered.
"If you can imagine standing on the surface of the moon near one of its poles, you would see shadows all over the place," said Paul Hayne, lead study author and assistant professor in the Laboratory of Atmospheric and Space Physics at the University of Colorado Boulder, in a statement. "Many of those tiny shadows could be full of ice."
After assessing the potential size of the traps, ranging from centimeters to kilometers, the researchers determined that permanently shadowed areas at both of the moon's polar regions could contain a multitude of these "micro" cold traps. In fact, they could be hundreds to thousands of times more abundant than large cold traps.
The moon could contain 15,000 square miles of permanently shadowed traps in a range of sizes that could preserve water ice, the researchers estimated. Previous estimates have put the estimate at about half of that -- at about 7,000 square miles.
"If we're right, water is going to be more accessible for drinking water, for rocket fuel, everything that NASA needs water for," Hayne said.
Previous searches for ice on the moon have been concentrated around the large craters at the poles, where temperatures have been measured as low as negative 405.67 degrees Fahrenheit.
Massive craters close to the lunar south pole include Shackleton Crater, which is several miles deep and about 13 miles across. And most of it is permanently in shadow.
"The temperatures are so low in cold traps that ice would behave like a rock," Hayne said. "If water gets in there, it's not going anywhere for a billion years."
By using data from the lunar orbiter and modeling, the researchers determined that the lunar surface resembles that of a golf ball.
Of course, actual proof of these ice-filled shadowy pockets will require future digging by rovers or humans on the lunar surface.
But future missions to the moon, like landing the first woman and next man near the south lunar pole by 2024 through NASA's Artemis program, could reveal more information.
Ahead of that, Hayne is also leading the Lunar Compact Infrared Imaging System, a NASA effort that will capture 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," Hayne said. "They could walk around and find one that's a meter wide and that might be just as likely to harbor ice."
