NASA’s 10-day there-and-back voyage around the moon was the make-or-break milestone for U.S. human spaceflight, which has languished in low-Earth orbit ever since Apollo 17 commander Eugene Cernan uttered these parting words on the lunar surface in 1972: “We leave as we came and, God willing, as we shall return, with peace and hope for all mankind.”

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It has taken more than 50 years to get back. The reason why is as cultural as it is political or technical. Peace and hope aside, the Apollo program was created by conflict, born out of the technological advances of World War II and the cold war era’s extreme anxiety over the terrifying prospect of nuclear annihilation. Without competition from the Soviet Union, which had launched the first human into space and was pursuing its own lunar program, Apollo might have been abandoned—or never even existed. Apollo 11, the U.S. mission that first landed humans on the moon, was the program’s high-water mark. With the Soviet Union outmatched, Americans, momentarily satisfied, moved on. Inertia kept Apollo going for six more moon missions before the program’s end.

Now collective Western anxiety over the rise of China’s rapidly advancing space program and desire to go farther into space, beyond the moon, are driving Artemis forward. If Artemis II had experienced serious problems or ended in failure, it would have delayed but perhaps not ended the ongoing U.S. lunar push, just as the tragic fire that took the lives of the Apollo 1 astronauts didn’t derail that program.

What remains to be seen is how far Artemis will go. With the program, NASA is aiming to build an enduring human outpost on the moon and even to travel onward to Mars. But none of that is a given.

Much work remains before any astronauts make a 21st-century footfall on the moon. There is no guarantee that either the U.S. timeline of a human landing in 2028 or China’s target of 2030 will be met. But Artemis II is a positive signal. By once again sending crews to the lunar vicinity and returning them safely to Earth, NASA has shown that some of the Apollo era’s faded glory can be rekindled—and may yet be surpassed.

But any geopolitical calculus doesn’t entirely capture all the motivations for going to the moon, which are as myriad as they are subjective.

For one, we go because it’s there—an extraterrestrial Everest to climb. For another, we go because of the thrill of exploration and discovery, feeding the curiosity that makes us human. Or perhaps we go because lawmakers—chief among them recent U.S. presidents and congressional appropriators—perceive the powerful pull of history, realizing they can become names for the ages while bolstering the aerospace industry in the process. Indeed, perhaps we go because of industry, to mine the moon or otherwise exploit its resources for profit, unlikely as it may be that this would be of equal benefit to everyone’s lives on Earth.

But I keep coming back to a reason so fundamental that it’s almost ineffable, a pull as sure as the moon’s gravity that compels the rise and fall of Earth’s tides.

It must be said: our lunar companion is, today, as much a part of our living world as every organism on Earth—and always has been.

Many cultures throughout history have declared as much in ways both mystical and spiritual. Yet the lunar rocks hauled back by Apollo astronauts confirm this truth in the cold light of scientific rigor: Earth and its moon share an astronomically unlikely origin. A Mars-sized protoplanet, Theia, by chance slammed into the proto-Earth 4.5 billion years ago, and the moon coalesced from a mix of each body in orbit around our wounded world. You and all life on Earth eventually spun out of that epochal collision, too. This means, among a great many other things, that atoms from Theia—essentially, from what became the moon—are in every cell of your body.

Earth without the moon would not be Earth as we know it but a different planet entirely, perhaps devoid of life. Our lunar companion still stirs the oceans, stabilizes our seasons and sets our days, marking the rhythms for our biosphere. Eons of otherwise-lost cosmic history can be found in its craters, their silent secrets never scrubbed away by earthly wind and rain.

There may yet be myriad other ways, scarcely realized, in which the moon shapes life on Earth and our planet’s grand cycles of history. Perhaps, much like the rockhounding crews of Apollo before them, American and Chinese astronauts alike will spark another era of world-changing discoveries with whatever they find in their lunar explorations.

Perhaps, indeed, the unifying message of this wondrous moment of “moon joy” is the multiplicity of explanations for its existence—the fact that the beautiful complexity of the moon’s influence on all of us is too great yet too subtle for any single answer to suffice.

The astronauts of Artemis II know this. Gazing on the moon from the closest anyone has seen it in a half-century, they all spoke of their sense of awe, wonder and joy—and their longing for Earth. Glimpsing the blue-green jewel of our planetary home, so small and distant, after arcing around the far side of the moon—a maneuver that had been set in motion by a six-minute “translunar injection burn” of Orion’s main engines in Earth orbit—mission specialist Christina Koch put it particularly succinctly:

“We hear you can look up and see the moon right now. We see you, too,” she radioed down to NASA’s Houston mission control. “When we burned this burn towards the moon, I said that ‘we do not leave Earth, but we choose it.’ And that is true. We will explore. We will build. We will build ships. We will visit again. We will construct science outposts. We will drive rovers. We will do radio astronomy. We will found companies. We will bolster industry. We will inspire. But ultimately we will always choose Earth. We will always choose each other.”