The following is an excerpt from Our Moon: How Earth’s Celestial Companion Transformed the Planet, Guided Evolution, and Made Us Who We Are by Rebecca Boyle.

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Our Moon: How Earth's Celestial Companion Transformed the Planet, Guided Evolution, and Made Us Who We Are

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The Moon is different.

It is like nowhere on Earth, which is a watery bubble improbably bursting with life in a universe of emptiness. The Moon is barren and has been throughout the four-and-a-half-billion-year eternity of its companionship with this planet. The Moon is silent. It plays host to no cricket chorus, coyote calls, or night wind sailing through pines. It is dry, at least on the outside. There are no waves lapping on shores, no soft rains, no snow. It is a crater- pocked wasteland that smells of doused firecrackers. The Moon is scorching hot during its long day, and freezing cold during its long night.

The lunar landscape is grayscale, but flecked with shades of tan, chocolate, beach sand, chalk, gold, spicy-mustard ochre, and, in the words of Apollo 11 astronaut Michael Collins, a “cheery rose” hue.

Sunlight on the airless Moon plays tricks on human eyesight, warping a moonwalker’s sense of crater depths and hillside angles, making tiny slopes look like vertiginous peaks. All is monotony. There is no blue, and there is no green. No sunlight scatters through a watery atmosphere. No lichens splotch the Moon’s rocks. No bacteria grow in its dirt to help plants flourish. Certainly, there are no birds overhead, ants underfoot, or any other kind of animal anywhere. On the Moon there is nothing and no one. Until the Apollo landings, no creatures ever looked up at the Moon’s black sky and wondered about their place in it all. No one ever stared up at the crescent Earth and thought about visiting. There is no culture, except the one we brought.

The Moon says nothing for itself, but it says plenty about us. We project our dreams and our fervor onto its mottled surface and it serves as a mirror, both figuratively and literally. It reflects sunlight and even Earth’s own light, ashen earthshine, back to us. We can see this phenomenon when the Moon is a crescent, and yet its full disk is just barely perceptible. The Moon is Earth in inverse, a desolate rock whose scars whisper of our world’s violent past and underscore its riotous gardens of color and life. The Moon contains only what we imagine it to contain. It harbors only what we berth in its seas.

Since the beginning of time, the Moon has controlled life on Earth and shepherded the human mind through a spectacular journey of thought, wonder, power, knowledge, and myth. But this frenzied, multifarious, Earthly history disguises the truth of the Moon. As vivid and lively as our history with it has been, the Moon itself is quiet, barren, and still.

This was not always the case: When the Moon was young, it was livid with energy and heat, a magnetic field, oceans of lava, and maybe an active crust like the one that warps and wrinkles the face of our world. But no one was around for this lively phase. The only Moon we have ever known is the spectral one in our sky, the two-dimensional one, the cold and silent one.

Nothing happens there, except the occasional arrival of an asteroid or the briefly violent puff of a crashed or landed spacecraft. Nothing looks up, nothing breathes, nothing hopes.

When Apollo 11 astronaut Buzz Aldrin walked on the Moon in 1969, he described his surroundings as “magnificent desolation,” an interpretation that has yet to be bested. It’s difficult to liken the Moon to anywhere familiar, because anywhere familiar is a place on Earth.

Even from orbit, Earth looks and feels like home. Astronauts report that staring down on our planet is one of the most exhilarating things about being in space. We belong here. Earth’s razor-thin atmosphere, cloud tendrils, green-carpeted continents, and deep ocean blues beckon us. Not so for the Moon, according to Collins, who orbited it alone in his spacecraft but did not walk on it. There is no comfort to the “withered, sun-seared peach pit out my window,” he wrote in his memoir, Carrying the Fire. “Its invitation is monotonous and meant for geologists only.”

Humans are sensory beings, and the Moon is a place devoid of any familiar sensory experience. If you were to visit, you might experience conflicting feelings of deprivation and overwhelm. Every time you went outside—in a spacesuit, of course—and every time you went back indoors and took off your gear, the Moon would bowl you over. You would feel lonely, hot, freezing, terrified, ecstatic, superhuman, and tiny, in a matter of moments or maybe all at once. Its topography, its innards, its atmosphere—everything about the Moon is different.

Apollo 11 moonwalkers Neil Armstrong and Buzz Aldrin were the first human beings to experience selenic discomfort. Moon dust covered their spacesuits and boots, and it soon covered much of the inside of their Eagle lander, too. The pair were so annoyed by it that they slept in their helmets to avoid breathing in Moon all night. On later missions, astronauts noticed the dust scratched their sun visors and damaged the seals on the rock boxes they toted home. Moon dust caused a form of hay fever, making astronauts’ eyes watery and itchy and their throats scratchy and sore. Unlike Earth dust, which is mostly made of organic material, Moon dust is all pulverized rock—and no water or wind exists to soften the dust grains’ edges. It was like breathing in sandpaper.

But the astronauts were lucky that this was nothing more than a nuisance. NASA scientists had warned the astronauts that Moon dust might be reactive in oxygen. Aldrin and Armstrong were told to be cautious about their contingency sample, a small scoop of Moon that Armstrong tucked into his pocket moments after stepping out of the Eagle. After coming back inside, Aldrin and Armstrong watched the dust carefully as the Eagle cabin pressurized. If anything started to smolder, they were supposed to open the hatch and throw it out. But both men were completely coated in it.

“The stuff seemed to stick to things and stay there,” Aldrin said. “There was no hope of getting that off.” If anything was going to ignite, it would be their suits.

The dust turned out not to be reactive in oxygen, but it did smell that way. The Moon has an acrid aroma, like fireworks that have just gone off. That is how Aldrin described the scent in the capsule after he and Armstrong came back inside from their brief sojourn and took off their helmets. Armstrong described it as “the smell of wet ashes,” like a campsite at bedtime after you’ve doused the fire. Apollo 17 astronaut Harrison “Jack” Schmitt has called it the smell of gunpowder.

The Moon is constantly bombarded by sunlight and radiation from other stars and cosmic sources, and it’s pummeled by asteroids in a process called “gardening.” All this action tears apart atoms in the “regolith,” the technical term for Moon dust. Lunar regolith is about 43 percent oxygen, so most of the atoms being shattered are oxygen atoms. The same is true
of gunpowder. When it ignites, chemicals in the gunpowder release copious oxygen, further fueling the blast. What the astronauts smelled was the lingering aftermath of atoms being torn apart by tiny invisible bullets of radiation.

This is still a matter of scientific debate in part because the Moon rocks don’t have a smell anymore. When a scientist opens a bag with a Moon rock today, no matter how carefully it was chipped and packed up for distribution by NASA’s Lunar Sample Laboratory, there is no scent of the unknown. No one can say for sure why the smell fades once the rocks are exposed to humans, and to Earth.

On the Moon, after you got used to the smell of constant fireworks, you would notice the unceasing dryness. The Moon is a parched place, and you would dearly miss the omnipresence of water to which you have been accustomed your entire waking life. It would tease you every time you saw Earth. However familiar and beloved our continents and their mountains, Earth’s land does not dominate the planet’s features; from a distance, the water is what stands out, a blue beacon of serenity and warmth.

For most of human history, people believed that the Moon had oceans, too. Astronomers through the centuries believed the Moon’s dark spots were actually lunar seas. Moon-fixated scientists in the seventeenth and eighteenth centuries believed this so fully that the list of features on its face are all named as oceans, lakes, and bays. The Sea of Tranquility, where Apollo 11 landed, was a real sea in the mind of Moon mapper Giovanni Battista Riccioli, the Jesuit priest who gave us the Moon’s modern nomenclature in 1651. Collectively, the dark spots are called maria, from the Latin for “seas.” In reality, as the Apollo Moon rocks taught us, the seas are vast plains of cooled lava.

While you would experience the Moon as a chalky, dry sea of emptiness, it does have water. Depending on what scientific instruments you believe, it has a whole lot. The trouble is that the water is locked up in the regolith as hydrated minerals, or may exist as ice that has been buried forever in craters that never see the light of day. Liquid water cannot exist on the Moon. With no atmosphere to keep water liquid, it would evaporate instantly, and its hydrogen would fly off into space. Any future Moon visitors hoping to access lunar water will have to be really talented chemists, skilled at liberating water from stone.

Excerpted from Our Moon: How Earth’s Celestial Companion Transformed the Planet, Guided Evolution, and Made Us Who We Are by Rebecca Boyle Copyright © 2024 by Rebecca Boyle. Excerpted by permission of Random House. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.