Earth’s moon looms. Fifty years after humans first set foot on the lunar surface, multiple nations and for-profit private companies are racing to go back.

For those hoping to put more people on the moon, many plans for future lunar missions hinge on harvesting available resources there. And the most resource-rich target seems to be the moon’s poles, where permanently shadowed craters act as “cold traps,” building up deposits of water ice from billions of years of comet and asteroid impacts—and also a possible active “water cycle” on the moon.

Aeons in the making, those reserves could be truly enormous in size, offering sufficient water ice for astronauts to survive and thrive, enabling a sustained human presence on the moon. Extracted from frosty craters, the ice could be used for manufacturing rocket propellant, fuel cells and radiation shielding—not to mention for producing potable water.

Then again, that trove may offer treasure of a different kind. Although its utility for human survival is clear, the ice may have immense scientific value as well, revealing hidden chapters of lunar history that could inform our knowledge of how life on Earth arose and evolved. Experts are now debating whether to give a cold shoulder to nascent plans for mining lunar ice—at least until its scientific potential is better understood.

Exploring the Moon, Hand-in-Hand

Laszlo Kestay, a geologist at the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Ariz., says lunar ice is of unquestionable research interest. Studies of the deposits in dark polar craters could conceivably provide new information about the long-term stability of the moon’s orbit, the nature and timing of impacts by asteroids and comets, and even past episodes of lunar volcanism.

“In principle, there should be no real conflict between in situ resource utilization and science, at least at this point in time,” Kestay says. But he notes, “it is essential to develop an improved scientific understanding of the ice on the moon before we are able to properly design in situ resource utilization strategies and technologies.”

If lunar polar ice deposits are tapped it could be a great example of a project where science and commerce go hand-in-hand. That is the view of John Rummel, a former NASA planetary protection officer, now a senior scientist at the SETI Institute in Mountain View, Calif.

“For their part, scientists view the many layers of polar ice as a record of past cometary and asteroidal impacts, shedding light on the long history of the Earth-moon system,” Rummel says. “But they need engineering expertise to be able to drill a core at 80 degrees Kelvin, which is quite cold.”

Conversely, Rummel says, “ice prospectors” will want to know what the ice is made of and whether it is of a high grade—that is, not too dusty or otherwise contaminated. “Some comets may have on the order of 5 percent cyanide in their cores,” he points out, “so lunar miners will have to be careful about product quality if they are going to sell it!”

Astrobiological Interest

Relatively little is known about the ice at the lunar poles, says Paul Lucey, a planetary scientist at the University of Hawaii at Manoa. “But it certainly has major scientific potential, depending on how it got there and when.”

In particular, Lucey says, any cometary ice entombed within a crater-based cold trap could be of significant astrobiological interest, possibly containing hints of how crucial ingredients for life first came to the Earth-moon system. Keeping that evidence relatively uncontaminated by future lunar landings could be important.

“There may be unique sites to preserve from the outset for scientific exploration,” Lucey says. As yet, however, there are no sufficiently detailed maps of ice distribution to allow the identification of critical sites. Lunar mining could create opportunities, he says, for sampling deposits that would otherwise be beyond the reach of a space agency's science exploration budget.

“If organic [materials] are present in the lunar poles, they represent an opportunity to field-test models of [chemical] synthesis that are proposed for comets and interstellar clouds, which in turn are thought to have been important in providing organic material to the early Earth,” Lucey speculates. Indeed, he says, there is no other off-world location in the solar system more convenient for conducting such studies than the moon.

Similarly, astrobiologist Dirk Schulze-Makuch, a professor at the Technical University Berlin, Germany, and an adjunct professor at Washington State University, argues that lunar ice may contain the only relics that we might find from the earliest evolution of life on Earth. “I think we should ‘go’ [to mine lunar ice], but definitely also analyze for any organics that this ice may contain,” he says. “That way we might be able to solve the riddle of how life originated on Earth.”

Science First

According to Jim Green, NASA’s chief scientist, current estimates suggest somewhere between one hundred million to two hundred million tons of water ice exist in the moon’s dark craters—which is something to be thrilled about. “Scientifically, we’re excited about it because we want to know how it got there … and did it happen all at once, or is it [still] happening today?”

By studying those permanently shadowed regions, Green says, future explorers could not only peer into the history of lunar impacts but also potentially make new discoveries about the moon's interior, such as the history of water and other volatile compounds in the lunar mantle. “It leads us to the scientific desire to go to these locations and bring back cryogenic samples to study in the laboratory,” he says.

Does that mean grabbing ice core samples from each sun-deprived crater on the moon and then saying all the rest of that water is off limits?

“My answer to that is no, not at all,” Green emphasizes. “We will want samples back and will probably get samples back before the mining industry pulls up and does their thing. They are going to wait for us to get a core and tell them what’s there. First of all, scientists don’t know, and they are going to want to know. It’s a tremendously exciting time. It’s all about doing the science first.”

Green recounts that the classification of the moon in terms of planetary protection dates back to the Apollo lunar landing program. After Apollo 11 astronauts traveled back to Earth from their historic moon voyage, they were stuffed inside quarantine housing—a specialized Airstream trailer. So too were the crews of the Apollo 12 and 14 lunar landing forays.

“When it was decided that there was no biological material in the lunar samples to worry about, the doors were opened to let the astronauts go home,” Green says. So the classification of the moon is “unrestricted Earth return” of lunar specimens.

But based on new lunar science observations, is there any consideration of changing that classification, and if so, what would be the justification?

If so, it would come from the United Nations’ Committee on Space Research (COSPAR) Panel on Planetary Protection, for which Green serves as the NASA representative. “Right now, there’s nothing that I see that gives us a pause about changing the classification,” he says.

Occupy the Moon?

So what is needed to get the best of both worlds, to utilize lunar ice for both sustainable exploration and for science?

Joanne Gabrynowicz, a professor emerita of space law at the University of Mississippi, notes this is an area of active international debate, despite the fact that the basic guidelines were created in the United Nations Outer Space Treaty of 1967. Gabrynowicz is a committee member co-author of a 2018 National Academies report on planetary protection policy that addressed how to identify and protect scientifically valuable areas.

If water ice on the moon was thought to be rich in past or present microbial life, for instance, it might be cordoned off and preserved for study. “From the science point of view, that makes a lot of sense,” Gabrynowicz says.

As recommended in the report, a formal international agreement is needed to address the question of protecting the moon as a resource for scientific studies, regardless of whether the exploration is being conducted by government or by private companies. Such an agreement could set guidelines for identifying and protecting sensitive regions of the moon based on recommendations from scientists, engineers and policymakers, and would be enacted through the United Nations. Its legal basis would rest on Article II of the Outer Space Treaty, which states that the moon “is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means.” To close off access to a section of the moon because it has scientific value, Gabrynowicz says, would amount to “occupation” under the Outer Space Treaty.

“That is why there has to be an international agreement,” she says. “It is not a diplomatic nicety. It is a legal necessity.”