A map of "cold traps" inside shadowy lunar craters at the moon's south pole (left) and north pole (right). Blue dots show locations where water ice may be present at or near the surface.

The moon is littered with patches of hidden water, NASA researchers have discovered.

That's great news for the agency's plans to send astronauts back to the moon, set up a permanent base there, and eventually use it as a stopping point on the way to Mars.

Those ambitions hinge on the ability to mine water ice on the moon and break it down into oxygen and hydrogen to make rocket fuel. Since it's extremely costly and difficult to launch enough fuel off of Earth to get astronauts to Mars, water on the moon will likely play a critical role in kickstarting a new era of human deep-space exploration.

"You start making gas stations in space. This really starts cutting your dependence on bringing all that fuel from Earth," Angel Abbud-Madrid, director of the Center for Space Resources at the Colorado School of Mines, previously told Business Insider. "That's really been what's holding us back from deep-space exploration."

Artist's concept of astronauts and human habitats on Mars.

Until now, NASA hadn't known how much water could be available on the moon, or how easy it would be to mine. But two papers published in the journal Nature Astronomy on Monday make the future of lunar ice mining much brighter.

One of the studies confirmed the presence of molecular water in the moon's surface dust for the first time. The other identified tens of billions of small, cold regions in shadows across the moon where the sun never shines and ice sits comfortably on the surface.

"Both, in different ways, would seem to indicate that there's more water available on the lunar surface than we've been thinking even recently," Leslie Gertsch, a geological engineer at the Missouri University of Science and Technology, and who was not involved in the studies, told Business Insider. "Whether it's mineable or not is another question."

A space plane detected lunar H2O for the first time

Experts had long thought the moon wouldn't be a safe place for water, since it has no atmosphere to shield its surface from the sun's radiation.

But scientists and their spacecraft have been picking up telltale signs of lunar water for the last three decades. First, they found hydrogen lingering over the poles. Then traces of water appeared in lunar-rock samples from the Apollo missions. Later, the Cassini spacecraft picked up signals for water as it glanced at the moon on its way to Saturn.

Finally, in 2018, scientists confirmed water ice sitting on the surface of the moon's poles. These reservoirs lie in shadowed regions called "cold traps" that sunlight can't reach.

But there was always a possibility that none of those discoveries were actually water as we know it — H2O — instead of a compound called hydroxyl (OH).

Researchers tend to use the word "water" to describe both compounds, but the oxygen and hydrogen molecules that make up hydroxyl form a much stronger chemical bond than those in H2O.

"If we wanted to extract hydroxyl from a soil to use it for a resource, it would take a lot more energy to break that apart, to create other things like breathable oxygen or water to drink for the astronauts," Casey Honniball, a postdoctoral fellow at NASA's Goddard Space Flight Center, said in a press briefing. "But with molecular water, if we have that on the moon and we can extract it, that makes it an easier process to get it to other compounds that we would want to use."

To find out whether the moon harbors molecular water or hydroxyl, Honniball hopped on a space plane.

NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA)

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a converted Boeing 747 souped up with a 2.7-meter telescope and the ability to fly into the stratosphere. That's high enough to avoid the atmosphere's distortion of infrared signals from the moon.

Honniball spent around nine hours in the plane, flying about 40,000 feet above the Earth. She detected the wavelengths of H2O and, surprisingly, they came from a sunlit part of the moon.

That means the water molecules are probably embedded in glass beads that make up about 30% of the lunar soil. Those likely protect H2O from the vaporizing powers of the sun.

Honniball doesn't know if glass across the entire moon contains water — it could be specific to the region she studied. Either way, though, water molecules embedded in glass beads would not be easy to mine.

"There's a reason why high-level nuclear waste is planned to be put into glass," Gertsch said. "Glass does not let stuff out easily."

Little shadows could harbor water across the moon

Mountains on the moon, seen by NASA's Lunar Reconnaissance Orbiter.

Until now, the best known caches of lunar water are those in the large, permanently shadowed regions at the poles — the coldest spots ever measured in our solar system.

But in digging through thousands of photos from NASA's Lunar Reconnaissance Orbiter, a group of researchers found smaller regions of permanent shadow littering the moon's surface.

Paul Hayne, a planetary scientist at the University of Colorado Boulder who led the study, likened the discovery to the process of "turning over a rock and finding all the gazillions of insects that skitter away." He estimates that there are tens of billions of these "micro cold traps" surrounding the moon's poles.

Hayne's team did not look for water in these regions, but previous research already confirmed the presence of water ice in the large shadows on the poles.

"If there's water in these larger cold traps, then there should be water in the smaller ones too," Hayne told Business Insider.

This means that mining machines could theoretically stay in the sunlight — and avoid extreme freezing temperatures — while dredging ice from micro traps.

"You could go to a place in these polar regions and stand in the sunlight and bend over, or use a tool to extract water from one of these much smaller shadows that's much more accessible," Hayne said.

All in all, Hayne's team estimates that shadowed cold-trap regions cover about 0.15% of the moon's surface.

The moon as viewed by NASA's Mariner 10 in 1973.

If these micro cold traps are filled with water, that would make moon mining easier, since they extend away from the poles and it's easier to land a spacecraft near the moon's equator.

But Gertsch warned that big questions about lunar ice remain. Although both of these discoveries are "enticing," she said, we can't really know the nature of the lunar ground until "we go up there and mess around."

NASA is sending a water-hunting rover to the moon's South Pole

An illustration of NASA's Volatiles Investigating Polar Exploration Rover (VIPER) on the surface of the moon.

To investigate lunar water up close, NASA is preparing to launch a drill and mass-measuring instrument to the moon's South Pole in 2022. Once there, it will try to harvest water ice.

Then in 2023, NASA aims to launch the VIPER (short for Volatiles Investigating Polar Exploration Rover), which will trundle over rocky terrain, drilling into sections of moon ice and soil for analysis. Over the course of its 100-day lifespan, the rover's main goal is to collect data for NASA to map out the moon's water resources.

An illustration shows Astrobotic's Griffin lunar lander deploying a ramp on the moon's surface.

Given their more accessible locations, Hayne's micro cold traps could be ideal targets for these missions.

Honniball's team, meanwhile, has requested 72 more hours on the SOFIA plane for further lunar observations.

But if NASA really wants to set up a moon-mining operation, it will have a lot more work to do.

"It takes more than one rover," Gertsch said. "You can't just send one prospector on a donkey out into the mountains and expect to design a mine from that."