Last week, upon leaving the president-elect’s office, Douglas Brinkley, a historian and conservationist, reported that Trump “was very interested in a man going to the moon.” Before that point, the entirety of Trump’s utterances of space policy consisted of two sentences: “Honestly I think NASA is wonderful!” and “Right now, we have bigger problems… We've got to fix our potholes.” Brinkley’s remark suggests he might be thinking about a moon base, an idea long-favored by Newt Gingrich, one of Trump’s advisers. The constitution of his transition landing team at NASA, which includes lunar advocates, would seem to bear this out.

The principal arguments for a moon base involve digging mines and building fuel depots. Though the moon lacks the resources to ever be truly self-sustaining, it only takes a few days to reach from Earth. If the U.S. decides that the goal of human spaceflight should be to gather resources, the moon and its quarry of helium-3 will be a compelling target. The isotope is extremely rare on Earth because of our magnetosphere. The moon has no such protection, and for billions of years it has collected the stuff by way of an unyielding fusillade from solar winds. There is an estimated 1.1 million metric tons of helium-3 on the moon. A mere 40 tons could power the United States for a year; if scientists are able to build a fusion reactor, we could shovel it into our nuclear power plants for centuries to come. There are also countless scientific questions that can be answered on the lunar surface. A telescope, for example, built on the far side of the moon and thus free of Earth’s ionosphere and radio interference would allow scientists to see the beginning of the universe.

Chris Carberry, CEO and founder of Explore Mars, a nonprofit Mars advocacy group, argues that far greater opportunities exist on Mars, and that a return to the moon might delay Mars settlement by decades. Mars has carbon, nitrogen, oxygen, and hydrogen—everything a colony needs to be self-sustaining. With those ingredients, you can do everything from manufacturing plastics to cultivating the soil. In other words, you can build a base on the moon, but a civilization on Mars. Moreover, Carberry says that the red planet has never been in a better position politically, culturally, or scientifically.

“Right now we have an unprecedented level of support for Mars exploration,” Carberry says. “Frankly it would be foolish to throw that away. There's a huge amount of support on Capitol Hill. The Senate just passed a transition bill with the strongest Mars language ever put into legislation. The House did a previous authorization bill with very strong Mars language as well. There are many years of bipartisan support for Mars—also for the moon, but the strongest emphasis is on Mars. That goes for industry as well. Boeing, Lockheed, Aerojet Rocketdyne, SpaceX, and others put quite a bit of effort into designing a mission architecture.”

American moon partisans owe a debt to Europe, which has tended the lunar flame during the ascent of Mars. Perhaps the most prominent moon advocate on Earth is Jan Woerner, the director general of the European Space Agency. Since assuming the post, he has argued persuasively that a “lunar village” is the natural successor to the aging International Space Station. It would be, in his view, a celestial point of harmony for a terrestrial species in discord. There is a problem, however: the Europeans have committed virtually no money to a moon village, and Russia, ESA's would-be partner in the venture, has no money to commit. They have already been forced to downsize their presence on the ISS due to costs, and have delayed plans for robotic exploration of the moon. (The head of the Russian space agency admits that Russia “does not have financial capabilities for advanced space projects.”) Lacking unity among member states, to say nothing of technology development and financial resources, what ESA really needs is for the United States to fund and spearhead such an effort. NASA's sights, however, are firmly fixed on Mars. With the presidential transition, however, and a new NASA director still to be appointed, lunar champions at home and abroad see an opportunity to abandon the Journey to Mars program and set sights a little closer to the Earth.

To that end, ESA is on a moon base public-relations offensive, from the light and easy (magazine spreads and aspirational illustrations) to bare-knuckled politics  (publicly pressing the NASA administrator on the issue.) The overt message from Paris, where ESA is headquartered, is: We're doing this. The subtext is: While NASA plans a fantasy mission to Mars that will never happen, the rest of the world will be driving moon buggies and mining helium-3. But ESA’s campaign is powered by handwavium, and for all the illustrations of lunar domes and our great big blue marble over the horizon, progress on the moon base ends at Photoshop. If the U.S. doesn’t build the base, it won’t get built.

Casey Dreier, the director of space policy for the Planetary Society, a nonprofit space advocacy organization, says that if any space agency really wants to land humans on the moon, let alone build a colony, there's no getting around the commitment to a program on the order of Apollo—a colossal commitment that ESA has not addressed.  

“First you’d have to see a commitment to hardware that could get humans to the moon,” Dreier says. “Soyuz [the Russian-built spacecraft] doesn’t get to you there.” Even if deep space hardware for multi-week missions existed, however, there's the more fundamental problem of actually getting it into space. “You would need a new heavy launch rocket or plans that use existing rockets for in-orbit assembly of hardware, and that's just to get to the moon.” (Only American rockets in development have the requisite lift.) There's still the most challenging part of the mission: the lander. “Even more basically,” says Dreier, “ESA has to come together formally and commit votes. If there was a serious project, member nations would commit funds and decide things like: What do you do there?”

The moon has always been part of NASA's Journey to Mars program. Though landing on the lunar surface is not part of the current plan, cislunar space—the 250,000 miles between the Earth and the moon—is essential. NASA calls it the “proving grounds,” and intends to develop that part of deep space to test life support and propulsion systems for any Mars expedition. Moreover, the Space Launch System (the colossal “Mars rocket” able to lift heavy payloads into space) and the Orion spacecraft for carrying astronauts into deep space are essentially holdovers from the Constellation program, the Mars space exploration initiative begun by President Bush in 2004 and canceled in 2009 by President Obama. The first stop on Constellation's roadmap was the moon, meaning SLS and Orion, both soon to roll off the assembly line, are moon-ready.

Carberry says that if we change focus to the moon, however ill-advisedly, we should still do so in the context of going to Mars. He points to the Apollo program as a good example of how not to frame a space mission. The first time NASA went to the moon, it did so based on single reason: to beat the Soviet Union. Once that singular reason was accomplished, there will little will to maintain momentum. The long-term goal—Here is what this is all building toward—never entered the public policy discussion.

“If you always have something beyond your current goal, it strengthens resolve to keep moving,” he says. “You strengthen your argument by making sure you have those longer-term goals—that this doesn't stop at moon. Hopefully it won’t come to that. If we can use the surface of moon within the framework of going to Mars, and we can stimulate commercial activity there, that's great, but if we put everything into the moon, we'll be stuck there for decades... Does US want to do a moon program forever? I don't know. Our advantage is clearly on Mars exploration.”

That advantage goes beyond national pride. NASA has been successfully landing spacecraft on Mars for 40 years. No other nation has succeeded in doing this even once. Exploring Mars is difficult, as the crashed ESA-Russia Schiaparelli EDM lander confirmed in October. NASA has established a cadence of Mars missions, each more complicated than the last, each developing Martian science and engineering with eventual human exploration in mind. As long as the Mars missions continue, the agency can iterate on its carefully accumulated institutional knowledge. If that knowledge is wasted and manufacturing partners spin down, the entire Mars apparatus will have to be regrown from zero. This is the same problem NASA now suffers even in its limited plan to send astronauts to cislunar space. Although SLS and Orion are very far along in development, it will still be another five years at least before a crewed mission can be attempted to lunar orbit, replicating what Apollo 8 did 50 years ago.

Wherever NASA is directed to go by the new administration will likely require a commitment that pushes the alternative back by decades. There’s simply no money in the NASA budget for both the moon and Mars. As the ISS demonstrated, building the thing—moon base or Mars colony—is the cheap part. It’s the operational costs that bog exploration down. Twenty percent of NASA’s budget goes to keeping the space station crewed and in orbit. A moon base will entail a similar such slice of the pie, which covers things like maintenance, ground support, technicians, engineers, physicians, launches, hardware, supplies, and food. You don’t maintain a moon base and gear up for Mars. Just the opposite: Going to Mars would specifically entail closing the moon base, which places Mars on the other side of lunar exploration, base design, base construction, base operations, base maintenance, and base divestment. NASA and world partners began work on the International Space Station began during Ronald Reagan’s first term. If we build a moon village, we’ll be there for a very long time.                                                                                                                         

Casey Dreier maintains that there is no correct destination for human spaceflight. “To me,” he says, “the least interesting argument in space exploration is ‘moon or Mars.’ It’s an important decision, but not an interesting argument. Mars is not objectively the only answer. The fundamental issue at play is what do we do that pays dividends as nation.” What dividends should we look for? Elon Musk advocates Mars colonization by defining Mars as humanity's failsafe—that once we settle and flourish on a second world, no matter what catastrophe might befall Earth, be it an asteroid or atomic devastation, the human species can survive. NASA frames Mars exploration in more hopeful terms, calling it a scientific endeavor through which we can learn about the evolution Earth and life. Either way, those are enticing and worthy goals. Astronauts can press boot prints into Martian soil in less than 20 years, but for that to happen, NASA must stay the course.