Andrea Mosie greeted me at the doorway to the moon with a wink. “Are you ready?” she asked. I had been warned about the technical procedures that would precede my visit, but I was not prepared for what I would see, and she knew it.

Only a few hundred humans have ever been to space. Only a handful have ever walked on the moon. But there is one other way to experience that other realm, and it is through a doorway at NASA’s Johnson Space Center in Houston. I entered a boringly tan federal building, walked up an undecorated flight of stairs, and reached the vault of our stars. It’s called the Astromaterials Acquisition and Curation Office, and it’s where you can meet 842 pounds of the moon, up close and personal. Mosie is their primary caretaker, and she promised to introduce me.

Only five people on Earth get to touch these rocks, contained in the Lunar Sample Lab, which holds the bulk of the material returned to Earth during the Apollo missions. If you’re the guy who picked up a rock from the lunar surface, they’ll make an exception, Mosie told me. But the curators who work with Mosie undergo lengthy training before they begin work preparing the rocks for scientists, who themselves spend considerable time getting ready to request just a few grams of moon.

Because of the Apollo program, which ran between 1962 and 1972, the glimmering orb that illuminates our nights and accompanies our days was finally made manifest. From its unique, disorienting point of view, the program revised our thinking about the universe, philosophically and scientifically. Apollo brought the moon down to Earth and Earth down to size. And the rocks in the Lunar Sample Lab are a testament to that transformation — a symbol and a source of new lunar knowledge.

Before we could enter the clean room, we had to dress head to toe in protective gear. Mosie took my clicker pen and handed me a fountain pen instead. The tiny metal springs in my clicker might shed a molecule of aluminum, she explained. No extra molecules are allowed in the clean room, lest they interfere with our measurements of the moon. But my paper notebook was just fine. We know there are no trees up there — any paper dust, anything organic, came from us.

We know this now, but back in the Apollo days not everyone was so sure. Until humans stepped on the moon, we could only imagine what it looked and felt like. Before Apollo, no one knew which elements composed the moon or whether its craters were formed by volcanoes or asteroid impacts. People could only guess at everything it had in store, which meant the Lunar Sample Lab, then called the Lunar Receiving Lab, had to be ready for almost anything.

At the time, several scientists even worried about protecting Earth from a lunar pandemic. After splashing down in the Pacific Ocean, Apollo 11 crew members stayed in a quarantine unit for three weeks to ensure they did not spread any lunar germs. The first bits of the moon were quarantined, too. Roughly a pound and a half were placed in containers with mice, fish, birds, shrimp, flies, worms, bacteria, and 33 species of plants and seedlings. Scientists watched to make sure none developed weird moon diseases or obvious mutations, just in case the rocks were poisonous.

In the Lunar Sample Lab a half-century later, we know that we only need to worry about contaminating the moon. After reluctantly handing Mosie my pen, I covered my shoes in fabric booties and shrugged white coveralls up over my clothes, allowing nothing in or out. I pulled on purple nitrile gloves, donned a hairnet, tugged knee-high, astronaut-looking white shoes over my bootied feet, and turned to face Mosie. She’s done this thousands of times, yet she laughed with me as I tried to shift my awkward bulk. She opened a door, and we stepped into an air shower. Any Earth dust on our suits was whisked away.

Finally, Mosie opened the entrance to the clean room, and I was surrounded by the moon. Most of it was locked behind a vault whose door came courtesy of the U.S. Federal Reserve. But the Lunar Sample Lab is an active geology lab, and bits of the moon were laid out everywhere. The moon was in cabinet drawers, displayed with special placards inside glass hoods, filling plastic baggies, perched unceremoniously in stainless steel baskets.

The rocks were so obviously not from around here. Most Earth rocks have a weariness, no matter where they’re found. They are molded by beach waves and rain, smoothed by wind and time, covered in lichen, surrounded by trees or grass. The moon rocks are nothing like that. They are jagged, blocky, crystalline. Some are inky black, and others are chalky, sparkling white. They look exactly like what they are, pieces of the shimmering moon brought down to Earth.

Mosie showed me some highlights, then led me over to a microscope. The moon people knew I had a favorite rock, and they took out Troctolite 76535 before I arrived. Apollo 17 astronaut Jack Schmitt used a rake to lift this rock off the moon in December 1972. He was walking in a valley called Taurus-Littrow, on the southeastern edge of the moon’s Mare Serenitatis, or Sea of Serenity. Schmitt is the only geologist to visit the moon, and he knew how to look for weird rocks. This little greenish, grayish specimen has been called the most interesting sample to come back from the moon.

It’s coarse-grained, and it cooled off slowly after being forged in the moon’s depths. The most recent studies on this rock show that when it was made, the moon had a rotating liquid core, as Earth does. That core endowed the moon with a magnetic field, just like Earth maintains today. But the moon is calm now. Its magnetic field is no more. Troctolite 76535 tells this story because it’s the oldest rock to come home during Apollo. It’s almost as old as the moon. And at 4.26 billion years of age, it’s almost as old as Earth.

Sharp, stiff, and flaked with a mineral called pyroxene, Troctolite 76535 was imbued with something ethereal. It was the moon beneath my eyes, not above them. Relics like this are what make Apollo as special today as it was in the ’60s and ’70s. The astronauts’ stories will live forever, but the pieces of the moon they brought back are the finer legacy.

The Apollo missions were the pinnacle of human exploration, the most stunning events of the second millennium. When President John F. Kennedy announced to Congress in May 1961 that Americans would land someone on the moon “before this decade is out,” there was no technology that could make it happen. NASA had no rockets powerful enough to get anything that far, not to mention computers small enough to travel on safe, habitable spaceships, which also did not exist. All of it was invented from thin air. From 1962 to 1972, Americans went from space-race losers to the nation that sent humans to the lunar surface, where they scooped up some of it for themselves.

Most important in that transition was the Apollo 11 mission, the first crewed moon landing, accomplished by astronauts Neil Armstrong, Buzz Aldrin, and Mike Collins between July 16 and July 24, 1969. Though Collins would not walk the moon, Armstrong and Aldrin would collect a total of 50 pounds of samples as they bounded across its surface.

The landscape was unlike anywhere on Earth. Its surface seemed to undulate, a trick of the terrain and the stark shadows cast by angled sunlight falling flat, with no atmosphere to bend it. The surface was sandy and soft, which Aldrin later compared to finely powdered carbon. The moon was not gray, but a landscape flecked with color. Apollo 10 astronauts sailing above its surface had noticed a range of browns, from light tan to milk chocolate. Aldrin remarked at one point that some rocks resembled biotite, a greenish-brownish-black substance. He joked that some even seemed to sparkle with purple. Analysis of lunar samples has since found volcanic glass in every color of the spectrum.

Toward the end of their short lunar sojourn, Armstrong visually weighed his collection bag and found it wanting. He dumped in nine extra shovelfuls of sand to fill it up. He could never have expected that the last-second scoops contained some of the most important rocks to ever come down to Earth. “Neil turned out to be the best field geologist on the moon, until Apollo 17, that is,” Schmitt, the field geologist who walked on the moon during Apollo 17, told me in 2019. “In 20 minutes, he collected some of the most interesting samples we got. Had we never had another mission, we would have gotten enough.”

Armstrong’s afterthought rocks were anorthosite, a low-density material that forms when minerals crystallize within molten rock. Their existence hinted that the moon was once bathed in an ocean of magma. “We knew right there that the moon would be a record of the early history of the Earth,” Schmitt explained to me. “That was not clearly understood before Apollo 11, but it was understood afterward, and now.”

Back on Earth, in Houston’s Lunar Sample Lab, it was possible to experience a version of the Apollo moonwalks. Before the astronauts took their samples, they photographed their orientation on the moon’s surface. The Lunar Sample Lab keeps that orientation, so the rocks are stored according to the way they were found. That way, scientists who study slivers of the rocks will know whether their samples were exposed to the void and bombarded by cosmic rays or protected by the moon. All this information provides a baseline for scrutinizing the rocks’ makeup, but it also endows the samples with a bit of mysticism. This is exactly what it looked like, up there, the orientation says.

After Apollo 11’s triumph, NASA’s confidence grew. Apollo 15 astronauts Dave Scott and Jim Irwin went to the moon with a wish list. Geologists were hoping for volcanic rocks, glass beads that form inside fire fountains, and other samples that would shed light on the moon’s youth. On their second day on the moon, the moonwalkers struck gold. They were taking samples of material ejected from a crater called Spur, inside the moon’s Mare Imbrium, or Sea of Rains, when Scott saw an unusual rock, which sat on what he would later describe as a pedestal of soil. He lifted it and dusted it off, and the astronauts recognized right away that the rock was special.

It was an anorthosite, and a big one. Reporters covering the mission were told it could help tell the story of the moon’s formation from a vast flood of oozing rock. They named it Genesis Rock. Genesis Rock was sitting in a pressurized box the day I visited. It was in a plastic baggie, and some crumbs filled the bag’s right corner: little bits of the moon that had started to flake off and fall apart. The crumbs were the perfect encapsulation of the new worlds Apollo brought to us: rocky, tangible, real.

The Apollo missions gave us something unexpected. They bestowed new knowledge about the universe and our place within it. Because of Apollo, the moon is no longer a faceless luminary in our imaginations. It became an awesome three-dimensional sphere, measurable and quantifiable. We’ve sifted it in our hands, its dead soils slipping through fingers pulsing with life.

Thanks to Apollo, the moon is here, among us: a bit of rock returned triumphant to tell us all our own story.

From the book Our Moon: How Earth’s Celestial Companion Transformed the Planet, Guided Evolution, and Made Us Who We Are by Rebecca Boyle. Copyright © 2023 by Rebecca B. Boyle. Published by Random House, an imprint and division of Penguin Random House LLC. All rights reserved.

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