The last time we put a human on the moon was 1972, over four decades ago. Since then we’ve learned a lot about it. Our probes and robots have revealed it’s a harsh, barren space boulder with a nightmarish environment. But, you know what else we’ve learned?

In the last 40 years we’ve also learned that while Earth and the Moon are very different in many ways, there are a lot of similarities, too—and these similarities can help us explore how to someday colonize our celestial cohort.

The Post-Apollo Years

The moon itself is a craggy rock over 2,000 miles in diameter. During the Apollo missions between 1969 and 1972, 12 American spacemen set foot on the moon, and hauled back a whopping 842 pounds of rock and soil samples. Those samples revealed that the moon’s makeup is similar to Earth’s. The rocks also revealed some of the moon’s possible origin: As one theory goes, a Mars-sized planetoid rammed into Earth 4.5 billion years ago, and a chunk of cosmic shrapnel flew into Earth’s orbit, becoming the moon.


Unfortunately, lunar exploration went out with bell bottoms, and pretty much vanished until the 90s. US machines like the Clementine probe and Lunar Prospector hinted at ice being on the moon—an enormous discovery that suggested the Moon, like Earth, is (or was) home to water. Later, the 2000s launched a lunar exploration renaissance of global proportions, with Europe, Japan, China, and India all getting in on the Moon action.

Eventually, the focus shifted from getting our warm-blooded, fleshy selves to the dark corners of the Moon. We wanted cold, metallic adventurers to go in our stead. Because while commonalities exist between Moon and Earth, in many ways, the two couldn’t be more different. That’s why colonizing the Moon must involve ‘bots.

Bring in the Robots

So, we managed to put humans on the moon. The last time was during the Nixon administration—an age of typewriters and Pong. Now we live in the world of global video calls and maglev trains. We seriously can’t get another person on the moon? What’s been the hold-up?


Here’s the thing. Or rather, things: There’s no air on the moon. Slight gravity. Barely any atmosphere. Temperatures can swing from 253 degrees Fahrenheit to minus 387 degrees Fahrenheit in a single day. Micro-meteoroids pelt the craggy surface. And since there’s no atmosphere, the sun’s UV rays would slice through us like a hot butter knife. Finally, back on Earth, there’s the political and financial red tape clogging up the progress of sending humans into orbit.

Then there’s the problem of regolith. Never heard of it? Here’s your TIL for the day: It’s mostly dust that powders the moon’s 40-mile-thick lunar crust, which is covered in boulders and rocks. It’s jagged and dangerous to equipment and humans.

Finally, big infrastructure efforts take years upon years, face relentless delays, and often yield empty promises. And when a huge infrastructure effort is taking place 240,000 miles away on a giant deserted rock, the bureaucratic and financial morass gets a million times murkier. Here’s where robots came in.

Sending ‘bots to the moon is far from new: The first one was sent up by the Soviets in 1970. But the moon has represented the kind of exploration humans are capable of, so debates have raged on as to whether we’re wasting time dilly-dallying sending machines, when we should be getting back to our Apollo roots and sending actual people.

“The debate over the relative merits of manned versus robotic exploration of space can be an emotional one,” citizen science site writes. “With the miniaturization of electronics, robotic probes will always be cheaper and more reliable than human spacecraft. However, many people think that the excitement of the space program depends on having human participants.”

The Yutu rover on its journey.

That hasn’t stopped space agencies around the world from continually ignoring or delaying human missions in favor of robots. China sent a lunar rover, Yutu, in 2013, for example. Yutu uncovered a lot of new information, including the fact that the Moon’s volcanoes might’ve been more volcanic the last 3 billion years than imagined.


In 2010, Japan announced plans to have a fully running, $2 billion robotic Moon base in place by 2020. Progress on that front is pretty much dead. A rep from JAXA, the Japanese space agency, told Gizmodo they “don’t have plans to send robots to explore the Moon at present,” though they do want a probe up there by 2020.

Thanks to these information-gathering robots, we have a better sense of the relationship between the Moon and Earth. But progress hasn’t been as fast as we’d like. There have been space program budget cuts, and Moon missions have been overshadowed by the more ambitious, romantic missions to Mars.

Assuming we space-faring countries finally get our Moon exploration act together, how can we better guarantee lunar colonization with humans will ever happen? Realistically, what needs to be done?

What We Need to Live There

How can we get humans back on the moon? And how can we stay there long-term? One key ingredient will make it happen. If we were talking about survival on Earth, the answer wouldn’t really surprise you. And on the Moon, we need the same, all-important elixir of life: water.


That’s according to Dr. Paul Spudis of Houston’s Lunar and Planetary Institute. He’s one of the most enthusiastic supports of Moon colonization around, and was deputy leader of the Clementine probe mission for NASA and an investigator for India’s lunar imaging radar project.

Spudis posits that there could be billions of metric tons of water hidden in the Moon. And that water is vital, just as it is on Earth. It’s a galactic Swiss Army knife.

“You can drink it, use it to shield you from cosmic radiation, [use it in] food and sanitation, and crack it into oxygen to breathe,” he says.” In the form of liquid hydrogen and liquid oxygen, it is the most powerful chemical rocket propellant known.”


“Water is the most useful substance in space,” continues Spudis. The obstacle? Figuring out the best way to find—and mine—the Moon water.

To do this, we (“we” meaning robots, at least at first) need to do lots of lunar experiments. What’s the nature of the Moon’s poles? Where is the water stored? We can answer those questions using robots—a couple of surface rovers, like Curiosity on Mars. These rovers can measure temperatures, slopes, surface properties, and the measurements of existing ice. Once we figure out a way to locate this vital resource on the Moon, the real progress can begin.

To survive anywhere, of course we need water and air. On the Moon, the trick is where and how to get it. Remember that regolith stuff, the lunar dirt? It’s 42 percent oxygen. If we can mine regolith of its oxygen and combine it with hydrogen, there’s our water ticket. We can also use that oxygen to, you know, breathe. And we can also use it in rocket fuel. (That’s a complex task, however, that involves heating that regolith to 900 degrees Celsius.)


Air and water aside, some believe that we can inhabit the Moon the same way our ancient ancestors inhabited Earth for millennia. Like Earth, the Moon has a ton of caves. Could the same principle work on the moon? A company called Astrobotic wants to send rovers to the moon to scope out those cave networks—those caves that could protect humans from all that radiation and raining meteorites.

Why Live on the Moon, Anyway?

Amid terrestrial problems like global warming, gaping income inequality, political unrest, hunger, diseases, and terrorists, why should we spend time and effort populating space? And why the Moon—sometimes it seems so passe, and that Mars (and its own moons) are getting all the funding and attention.


First, yes, it makes sense to want to colonize Mars, because it is more similar to Earth than the Moon. But the Moon comes with advantages, too: The obvious proximity to Earth, for one. If disaster strikes for Moon-dwelling humans, help is only 200,000-odd miles away. A one-way trip to Mars is months long.

There’s also something poetic, something special about the Moon, Spudis points out. “The story of the Moon is our story—Earth and Moon are actually a single, double-planet,” he says. “Things happening in this corner of the universe happen to both Earth and Moon, but the Moon (being an ancient, fossilized world) preserves a record of this history, one that has been erased on the dynamic, active Earth.”

While more countries are turning their attention toward Mars (and beyond), we really should refocus on the celestial body closest to us. We should give lunar probes specific water-finding objectives, and follow through on getting humans back to the Moon. Sure, we may not ever be able to live there—Mars might be better for that—but we can at least build a lunar base that serves as a research center and hub for star-skimming travel. The Moon might be the most realistic planet(oid) we can conquer. After all, we’ve done it before.


Corrections: An earlier version of this post said the moon was 1,000 miles wide. That’s the radius—its diameter is over 2,000 miles. Also, Yutu launched in 2013, not 2007.

Top image: Moon surface via JAXA