Cassini was crashed into Saturn, Opportunity sits covered in dust. The shuttles were dispersed to museums, and Kepler was shut down to remain in its Earth-trailing orbit, hunting exoplanets no more. And soon, the International Space Station will join the litany of retired NASA missions. When its time comes, in 2030 — unlike Mir before it, which was de-orbited so it would burn up in the atmosphere — the I.S.S. will fall into the sea.

The I.S.S. will depart an orbital environment significantly different from the one in which it was built, between 1998 and 2011. The number of satellites in orbit has multiplied more than tenfold since ’98, to approximately 8,500, and those accumulating orbiters traverse a sky littered with a tremendously large number of bits of human-made space debris, many too small to be tracked. The difference isn’t just the crowding, though. How we use, and think about, orbital space has been transformed.

A promotional video made by Deloitte puts it concisely and directly: ‘‘Have you ever looked up at the night sky with curiosity, wondering what’s out there? Here’s an answer that might surprise you: Business opportunities.’’

Idealists may cringe, and not only because the video begins with ‘‘Space, the final frontier,’’ a phrase that already belongs to someone. But Deloitte is right when it says, ‘‘Space has never been more accessible or rife with potential.’’ In terms of accessibility, technological and financial barriers to getting a satellite into orbit have plummeted. NASA outsources its resupply missions to commercial operators; the I.S.S. will soon sport a commercial module; and the seeds of space tourism seem finally ready to sprout. And in terms of potential? The potential for wonder and scientific discovery in space is there as it ever was, if you seek it. But there is a new potential, rising as the star of the I.S.S. sets. As the Deloitte video puts it: ‘‘We are at the dawn of a new era, where exploration gives rise to economics, and possibility turns the corner toward profitability.’’

Earth orbit is no longer the realm of innovation and discovery. It’s a resource up for grabs, and it is being grabbed with impunity. Deloitte projects a possible $312-billion-a-year economy in low Earth orbit by 2035. ‘‘We are on the cusp of enabling a vibrant LEO economy,’’ the company declares, ‘‘provided the right investment, incentivization and intervention efforts occur.’’ And of course Deloitte offers its services to grease those efforts.

The commercialization of LEO is in some ways proof that the I.S.S. has succeeded in its mission. One of the station’s stated goals is to facilitate deep-space exploration, with research into new space technologies and astronaut safety. Now NASA turns its sights to those deeper-space aims: returning to the moon in, hopefully, 2024, and putting a human on Mars at some point after. If you squint into the distance, an interplanetary future for humanity is in sight. But for all that the moon and Mars are targets for eventual future human settlement, the relative ease of reaching our own planetary orbit has already expanded our grasp into space. We’re there — for better and, undoubtedly, for worse.

When the first segment of the I.S.S. was launched, in 1998, there were about 600 satellites in orbit, a bit more than 200 of which were circling in low Earth orbit. Almost all of those were government satellites, both military and nonmilitary projects — space science, weather observation and so on — and almost all from the United States and U.S.S.R. LEO stretches up to about 1,200 miles above Earth’s surface. It’s where Sputnik flew, and the space shuttles, and where Hubble orbits still today. But when businesses started launching satellites, they focused on geosynchronous orbit. Much higher than LEO, at roughly 22,000 miles above Earth, a satellite in geosynchronous orbit has a consistent view of one hemisphere of the planet; it’s only in the last decade or so, with changing approaches to telecommunications and imaging in orbit, that commercial activity in LEO took off. In the 1990s, in fact, with the end of the Cold War, the number of satellites in LEO dropped for a bit. But all the advances in technology that the Cold War spurred — from solar power for satellites to global telecommunications — wouldn’t sit fallow for long; there was science to do, and profit to generate.

The astronomer Jonathan McDowell studies black holes, but he has what he calls a second life, studying and keeping an archive of the history of the space program, cataloging every piece of equipment we have launched and tracking those objects’ lives in orbit. ‘‘I’ve tried to be the chronicler of what humanity has done in space,’’ he says. McDowell sees a few ways to frame the story thus far of humanity in space. One way is through the shifts around whose satellites dominated orbit — from the superpowers in the 1950s and ’60s to a more broadly distributed international era in the ’70s and to the ’90s, when corporations began actively launching satellites to support and expand their operations, like constellations of telecommunication satellites. Around 2003, we entered what McDowell calls the democratic era, where technological advances made it so that almost anyone — an Earth-imaging company, say, or a university research lab — could launch a satellite.

Another way to see the story is in the shifting demographics of objects in space. For the first few decades after Sputnik, almost everything in orbit was owned and operated by a government, whether for military or civil purposes. From the 1980s to the 2000s, McDowell says, the balance was split roughly evenly among military, nonmilitary government and commercial. But in the past decade it has become, as he put it, ‘‘commercial and, oh, there’s a little bit of the other stuff.’’ Especially in the last five years, commercial satellites have come to dominate low Earth orbit, primarily through the introduction of satellite megaconstellations.

It’s a pleasingly astronomical name for such a problematic technology. The best known and most plentiful of these constellations come from SpaceX’s Starlink, Elon Musk’s space-based broadband provider that comprises, so far, almost 5,000 satellites in the lower realm of LEO. Other megaconstellation projects in the works come from Amazon and OneWeb, and many more companies and nations say they intend to follow Starlink’s lead. Starlink itself has projected a future in which more than 40,000 of its satellites will be circling the planet.

There’s not much unusual about these satellites but their numbers, which even now, let alone at 40,000, are staggering. While a single satellite crosses the night sky like an uncannily smoothly shooting star, Starlink satellites are often seen in ‘‘trains,’’ roving the sky in linear formation. Launched in batches of 50 to 60 at a time, they’ve already come to dominate the orbital census, rapidly accelerating crowding in LEO.

The problem with crowding is that it raises the risk of collision. A body in LEO moves at 17,500 miles per hour; any slower and it will fall back to Earth. And orbital bodies don’t move in orderly parallel lanes; their paths intersect. In 2009, a defunct Russian satellite and an active one run by the American communications company Iridium collided about 500 miles above Siberia. That single collision created more than 2,000 pieces of debris — and that’s only the pieces that could be tracked, at about four inches or larger. Thousands or tens of thousands of smaller fragments likely remain as well.

In the wake of this collision, various U.S. government agencies took on the responsibilities of space traffic control, tracking satellites and known large debris, alerting operators when a close call is coming. (Many satellites now have onboard propulsion systems, enabling evasive adjustments to course.) But while there hasn’t been another major collision, all the debris and junk that’s still up there poses a tremendous threat.

The most feared outcome of orbital crowding is Kessler Syndrome, named for the former NASA scientist Donald Kessler, who, in a 1978 paper he wrote with his supervisor, Burton G. Cour-Palais, described a scenario in which LEO becomes so crowded that collisions cascade until orbital space is unusable. ‘‘You can’t send up new satellites and expect them to function if they’re flying through a field of bullets all the time,’’ the astronomer Samantha Lawler, who studies outer-solar-system objects, and lately satellite pollution, told me. McDowell said, ‘‘We haven’t gone into full ‘dodge’ems’ yet, but it’s very clear from the rate of false alarms, near misses and minor collision-impact events that things are skating on the edge.’’

The possibility of collision isn’t the only problem with cramming low Earth orbit past capacity. Starlink satellites are already hampering astronomy research done from ground-based telescopes (and even Hubble) with visual occlusions and radio noise; the ambient light scattering off all those extra bodies also risks corrupting the darkness of night. The scientific and cultural resource of the night sky is in danger of being extinguished.

The archaeologist Alice Gorman studies the human presence in orbit through the lens of ‘‘space junk.’’ ‘‘If Earth orbit is going to be managed appropriately, we need to consider it an environment, not just the empty vacuum of space into which these objects have been put,’’ Gorman told me. ‘‘The thing that’s extraordinary is, after all of the discussions, for decades, about the problems of space junk, all of the respective national authorities are just granting licenses, without any coordination or without any other peers, without any consideration of what it’s going to mean.’’

The culprit is the obvious one: unfettered profit-seeking. ‘‘If you look at low Earth orbit right now,’’ Gorman said, ‘‘the story that it tells is of hypercapitalism overtaking all other values to the point where the promise of profit by these megaconstellation operators overrides every other consideration, including making sure that Earth orbit is usable for future generations.’’

When Deloitte calls space a frontier, they’re not just echoing ‘‘Star Trek’’ or J.F.K.’s motivational calls for the moonshot; they’re also invoking a metaphor and a history that is far more fraught than they seem to recognize. ‘‘The frontier metaphor,’’ wrote the anthropologist Lisa Messeri in a 2017 article in Slate, ‘‘sets up outer space as a passive landscape with no purpose other than human sustenance.’’ And when we see a landscape — or spacescape — through that familiar lens, we tend to replay familiar mistakes.

In a chapter on space junk in a 2020 anthology, Gorman offered a new way to see human detritus in orbit. In the shell of orbital space that envelops the world, she wrote, ‘‘interplanetary dust mingles with the machine dust derived from the decay of human-manufactured materials under the harsh conditions of high-energy particles, micrometeorites, atomic elements and collision with other space debris. This dust mix is the archaeological signature of a space-faring species.’’

It is archaeology seen in real time, a calling card of sorts to the cosmos: Here on Earth, we have transcended the boundaries of the planet. With our scientific inquiry, with our daily business, with inhabitation by half a dozen or so people at a time, we have taken the first step toward an interplanetary existence. With ingenuity and desire, we have extended the environment of our planet into space.

In his 1937 mystical sci-fi novel ‘‘Star Maker,’’ Olaf Stapledon writes of ‘‘chrysalis worlds’’ that struggle against spiritual growing pains: ‘‘They were always behindhand, always applying old concepts and old ideals inappropriately to novel situations.’’ We are one of those worlds right now, on the cusp of a cultural transformation that indeed demands new thinking. How can we expand our reach into the cosmos without recapitulating so many of the mistakes we’ve made on Earth? There’s no promise we won’t fail, but it’s worth it at least to deliberately ask: What kind of space-faring species do we want to be?

Jaime Green is the series editor of “The Best American Science and Nature Writing” and the author of “The Possibility of Life: Science, Imagination and Our Quest for Kinship in the Cosmos.”