MOFFETT FIELD, Calif.—Earth’s nearest neighbor, the moon, is far from being a “been there, done that” world in space science and exploration. That’s the message from scientists and engineers at NASA’s Lunar Science for Landed Missions Workshop, recently held here at the space agency’s Ames Research Center.

Between 1969 and 1972 a dozen U.S. astronauts voyaged there to scout stretches of the desolate, crater-pocked landscape as part of NASA’s Apollo program. But almost half a century after those fleeting forays, humans have yet to go back. Now a rising tide of spacefaring nations are poised to visit (or revisit) the moon, among them European countries, China, Russia, Japan, India and, of course, the U.S.

Calling them back is the fact that, of all destinations in the solar system, the moon is not only the most accessible but also one of the most scientifically interesting. Thought to have formed shortly after Earth itself from debris ejected by our young planet’s collision with a Mars-size protoplanet, the moon has been witness to nearly 4.5 billion years of our world’s, along with the solar system’s, history. Impact craters and trace elements captured on its airless surface record processes that also shaped Earth’s early years, but were wiped out by our own planet’s geologic processes. Precisely because it is so close, so inert and so dead, the moon may be the best place in the solar system to go to answer the question of how and why Earth became so active and alive.

Lunar scientists at the Ames meeting presented detailed ideas about using the moon as a platform for Earth-observing studies and astrophysical observations, and as a proving ground for new technologies and international collaborations to bolster exploration elsewhere. Volatile materials such as water ice in deeply shadowed craters could be turned into oxygen and rocket fuel, and may also offer pristine records that could unlock otherwise-hidden eras of lunar and terrestrial history.

It Takes a Village

“The scientific community wants to go back, and go back anywhere. Forty-five years is too long to have to wait,” says Greg Schmidt, the workshop’s prime organizer. This time it’s not a cold war–style lunar race between two hostile superpowers, he insists. Instead, now “the whole world is interested in the moon.”

James Carpenter, a strategy officer in the European Space Agency’s (ESA) Directorate of Human and Robotic Exploration, says China’s moon plans are particularly ambitious. Carpenter has been a leader in discussions between European and Chinese scientists to jointly study samples set to be robotically returned to Earth next year as part of China’s Chang’e 5 lunar mission. “In China they have been investing tremendously in the infrastructure for sample analysis,” Carpenter says. “Potentially, they have the best laboratories in the world. I think they are investing in their future.” The ESA is also working with Russia on that country’s Luna 27 robotic lander, slated to plop down in the moon’s south polar region in 2022.

This international moon engagement is a prelude to what ESA Director General Jan Wörner describes as a “Moon Village.” The vision is to combine the capabilities of different spacefaring nations into an international lunar base, Wörner says. The project would use robots as well as astronauts to perform scientific studies, while perhaps also bolstering business ventures such as lunar mining or space tourism. The Moon Village concept as described by Wörner “is an idea which is shared quite widely by most countries,” Carpenter says. “My expectation is that it’s going to happen.”

A Lunar Gateway

Whereas the U.S. is not a formal partner in the nascent Moon Village project, its independent plans could be a crucial stepping-stone for international lunar return. On the heels of a new Trump administration directive on sending NASA astronauts back the moon, the agency’s soon-to-be-released 2019 budget proposal may well lay out details about how it plans to get them there. One idea on the table is a Deep Space Gateway (DSG), a  lunar-orbiting mini space station for astronauts that could support missions to the moon’s surface and other deep-space destinations.

“If it’s deployed, the DSG can provide an orbiting base for human-assisted sample-return missions to the lunar far side, which is a completely unexplored region of the moon,” says David Kring, a senior staff scientist at the Lunar and Planetary Institute. With or without the DSG, Kring notes, a multiagency task force—made up of the ESA, Canadian Space Agency and Japan Aerospace Exploration Agency—is studying the engineering requirements for operating multiple robotic landers and rovers on the moon as well as the best approaches for blending human and robotic exploration.

Kring and his colleagues have already identified high-priority science and exploration sites on the moon. These include the Schrödinger Basin, a relatively youthful crater within the larger South Pole–Aitken Basin, which is thought to be the moon’s oldest impact crater. Visiting Schrodinger, Kring says, could allow scientists to retrieve and study both relatively young and very old lunar material from a single site.

A Five-Year Plan

In human-assisted sample-return scenarios, Kring says astronauts on the DSG would telerobotically drive a rover and share its science functions with mission controllers back on Earth. In that type of venture a robotic ascent vehicle would carry the collected lunar surface samples to the gateway. Astronauts would then transfer the samples to NASA’s in-development Orion spacecraft and tote those collectibles back to Earth for detailed study.

Kring also points to another mission scenario that details a five-year campaign of five human moon landings starting in 2028—a plan prepared by members of the International Space Exploration Coordination Group (ISECG). The proposed sites include: Malapert Massif, South Pole/Shackleton Crater, Schrödinger Basin, Antoniadi Crater and the center of South Pole–Aitken Basin. The DSG could support this undertaking, Kring says; his group is already designing excursion routes for astronauts at each of the five landing sites as well as navigation paths for rovers trundling between them.

“It is essential that the United States redevelop the capability for deep-space exploration,” Kring says. “We should strive to achieve a sustained exploration program in which we push beyond the boundaries of low Earth orbit—our current capability—and Apollo, a historical, short-duration deep-space capability.”

A Gateway—or a Detour?

But not everyone is riding high on the DSG as now envisioned. “You can put lipstick on a pig, but it’s still a pig,” says Clive Neal, a lunar scientist at the University of Notre Dame and co-organizer of the recent NASA moon meeting. He believes the DSG “needs to be reformulated” and would do little for human space exploration if implemented according to current plans. Those call for the cislunar outpost to be occupied by humans only about 30 days per year, a period Neal says is too short for a robust exploration agenda. Carrying out lunar science from the DSG could also be a challenge due to the orbits now being considered for the facility, he adds. A number of potential DSG orbits have been proposed—even the prospect of the facility being moved between orbits as needed for different missions. But so far, the orbits deemed most desirable tend to sacrifice scientific returns in favor of easier, more efficient “stationkeeping.”

Neal says a reusable moon lander (rather than a DSG) should be considered the most essential component for both human and robotic missions. “Science from the gateway will be less than from the surface. If the Gateway can be used as a refueling station, then it may be useful for establishing cislunar infrastructure that could stimulate private enterprise,” he says. “If it doesn’t, I think we have missed an opportunity.”

NASA needs to lead the human exploration of the moon, Neal believes—otherwise China will and the other space agencies will follow. “This is another chance for the United States to lead the world to the moon and beyond,” he says. “If we don’t grab it this time, we will be left behind and yet another opportunity will be missed.”