Will Increasing Traffic to the Moon Contaminate Its

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News in focus DANIEL RUTTER/NASA AMES RUTTER/NASA DANIEL NASA’s VIPER rover will be equipped with a one-metre-long drill to mine for ice below the Moon’s surface.

missions to the Moon’s south pole, starting with robotic landers in 2022. WILL INCREASING TRAFFIC Last week, a report from the influential US National Academies of Sciences, Engineer- TO THE MOON CONTAMINATE ing and Medicine (NASEM) argued that space agencies need to prioritize what science they ITS PRECIOUS ICE? want from the lunar poles in order to explore them effectively. The international Committee Scientists seek guidance on exploring on Space Research (COSPAR), which outlines best practices for space exploration, is also frozen caches at the lunar poles responsibly. evaluating the situation, and will decide in the coming months whether to issue new guid- By Alexandra Witze The ice is important to scientists for various ance for spacecraft going to the Moon. NASA reasons. Some want to analyse pristine sam- is waiting for COSPAR’s decision, and will then ith its lunar sample-return mis- ples to unlock clues to how and when Earth probably update its own regulations on how to sion last month, China kicked and the Moon accumulated water billions of visit the Moon responsibly. off a new surge in visitors to the years ago. Others want to mine the ice as fuel As Moon exploration ramps up, “we have Moon. At least eight spacecraft for rockets at future lunar bases. an obligation to do no harm to future science from nations including Russia, Explorers now face a complicated choice. investigations”, says Lisa Pratt, the planetary- WIndia, China, Japan and the United States are Do they start digging right away, to work out protection officer for NASA, who is based at set to touch down on the lunar surface in the the processes by which they’ll mine the ice? the agency’s Washington DC headquarters. next three years. Or do they proceed slowly, to preserve the sci- The question is, “How do we get this right?” For the first time ever, several of the upcom- entific record encoded in the ice? “Right now, No spacecraft has ever directly probed the ing missions will explore some of the Moon’s we’ve got some scientists saying we can’t go Moon’s poles and the ice that lurks there. China most scientifically intriguing areas — those anywhere near it because we’re going to ruin is planning a Chang’e-6 mission that might visit at its poles. Researchers are excited about it,” says Clive Neal, a geoscientist at the Uni- the Moon’s south pole, potentially scooping studying water that lies frozen in shadowed versity of Notre Dame in Indiana. “And others up ice and rocks and returning them to Earth craters in these regions. But they worry that say we need it, so we’re just going to go for it.” as early as 2023. It would be the successor to increased traffic to the Moon might contami- These tensions need to be resolved soon Chang’e-5, which collected rocks from the nate the very ice they want to study. — especially as NASA plans to send a series of Moon’s mid-latitudes last December. Japan

and India have also been discussing a robotic LUNAR ICE CACHES pristine samples of ice before traffic to the mission to the lunar south pole, as have Russia An analysis of the Moon’s poles suggests the places Moon picks up. Such a mission would tell them and the European Space Agency (ESA). (marked in dark blue) where ice could be most easily exactly how precious the ice’s scientific record mined by future lunar explorers. And then there’s NASA. Under US President is — and whether mining activities should be Donald Trump, the agency has been preparing Accessible ice predicted postponed, says Esther Beltran, a space sci- a suite of missions to the Moon. According to Less More entist at the University of Central Florida in current plans, NASA would send two robotic North pole Orlando and a co-author of the paper. landers to the south pole in 2022, followed by 80° NASA doesn’t currently have funds allocated a larger robotic rover, called VIPER, in 2023. for an origins-first mission, and continues to It would sink its one-metre-long-drill into the plan on sending multiple spacecraft to lunar lunar dirt to mine for ice. As early as the fol- polar regions. But the agency is listening lowing year, humans would arrive and begin 85° to scientists who are concerned about get- exploring icy craters, possibly collecting ice ting it right and intends to move carefully, and flying it, still frozen, back to laboratories says Pratt.“We need to balance the drive for on Earth for study, said a NASA report released resource utilization with the need for scientific last month. discovery and knowledge,” she says. Meanwhile, if COSPAR adopts new guide- Course collision lines for lunar exploration, NASA and the space The possibility of explorers contaminating agencies of other nations probably will, too. lunar ice is a problem no one anticipated five COSPAR’s current guidelines ask nations to decades ago, when Apollo astronauts became keep a list of all organic materials — such as the first humans to walk on the lunar surface. carbon composites, paints and adhesives — At the time, researchers thought the Moon was aboard missions headed for the Moon. Hav- bone dry. Only in the past decade or so have South pole ing that kind of list helps to alleviate concerns they realized that there is water in many places, -80° about contamination, says Kminek, because including frozen in dark polar craters1. it tells scientists exactly what sort of human- All this water could have arrived on the made material has entered the Moon’s envi- Moon by means of water-rich asteroids or com- ronment. One possible change might be for -85° ets, or by the solar wind bombarding its sur- future missions also to keep a list of the gases face. Some of it might have come from inside that they would potentially emit from their the Moon, spewed out in volcanic eruptions Cabeus crater rockets or life-support systems. from a water-rich interior. The ice inside the sunlight-deprived craters Decisions, decisions at the Moon’s poles might have accumulated Shackleton crater As these discussions continue, however, some over billions of years. If so, it holds a record scientists aren’t too worried about contami- not only of the Moon’s early history, but also nation issues. Neal and others note that water of Earth’s. The Moon probably formed when a vapour from rocket exhaust settles only as a giant object slammed into the newborn Earth thin layer on the topmost part of the Moon’s some 4.5 billion years ago, kicking up debris surface — so it wouldn’t take much work to dig

SOURCE: KEVIN CANNON SOURCE: that coalesced into the Moon and intimately below it to reach undisturbed ice beneath. linking their histories. On Earth, geological Last week’s NASEM report also notes that the activity, including plate tectonics, has erased time2. Even after 2 lunar days — 2 months on risk of contaminating buried ice is low. And much of the record of the planet’s early history. Earth — some 30–40% of the rocket’s water Kevin Cannon, a planetary scientist at the But the Moon has no such activity — a perfect would still be present, mostly frozen on the Colorado School of Mines in Golden, thinks study subject. night side of the Moon. “The main takeaway that the small amounts of contamination “The history of the Moon’s water provides was, the water vapour really goes everywhere,” introduced by exploring the Moon’s ice are a lot of clues to how the Solar System has says Prem. So the Moon’s polar ice has already far outweighed by the scientific advances of evolved through time,” says Ariel Deutsch, a been contaminated by past explorers. figuring out where and how all the ice is distrib- planetary scientist at NASA’s Ames Research COSPAR, the international group, has been uted. He has been mapping where the largest, Center in Moffett Field, California. asking hundreds of planetary scientists how most accessible caches of ice might be3 (see Because of the importance of the Moon’s ice, much they worry about lunar exploration ‘Lunar ice caches’). many researchers are cautious about how to potentially interfering with science at the Others have put forward several ideas for explore it. In particular, some have been exam- poles. More than 70% who responded to a sur- protecting the lunar ice. One proposal is to ining the possible contaminating effects of vey in 2020 said they were concerned that con- preserve one of the Moon’s poles for science rocket exhaust on the frozen caches. tamination could compromise the scientific while opening up the other for mining and Parvathy Prem, a planetary scientist at the record held in the Moon’s ice, says Gerhard exploration. “One thing we need to do is to Johns Hopkins University Applied Physics Kminek, the planetary-protection officer make sure we are far-sighted,” says Prem. “Who Laboratory in Laurel, Maryland, and her col- for ESA in Noordwijk, the Netherlands, and knows what sort of science people generations leagues last year simulated a medium-sized vice-chair of COSPAR’s planetary-protection in the future might want to do?” lander arriving at the Moon at 70º south — a few committee. hundred kilometres from the ice-filled craters In a white paper submitted to NASA, 19 sci- of the south pole. The simulation showed that entists, including Prem and Deutsch, propose 1. Li, S. et al. Proc. Natl Acad. Sci. USA 115, 8907–8912 (2018). even though a rocket would not release much what they call an ‘origins-first’ mission to a 2. Prem, P., Hurley, D. M., Goldstein, D. B. & Varghese, P. L. J. Geophys. Res. Planets 125, e2020JE006464 (2020). water, the water it does release would spread shadowed crater at one of the Moon’s poles. 3. Cannon, K. M. & Britt, D. T. Earth and Space Science 7, all around the Moon and stay there for some The goal would be to collect reasonably e2020EA001291 (2020).