What Exactly Is Space Junk—And Can It Be Cleaned Up?

Litter isn't just a problem here on Earth.

By its very definition, space should have a lot of, well, space. And while it does, there’s also a lot of something else these days: junk. This interstellar litter isn’t naturally occurring. Like the junk that’s choking our oceans and overtaking our land, it was put there by humans and is the result of a very specific mix of innovation and carelessness. Space junk is out of sight so most people don’t even know it’s there…but that doesn’t mean it’s not a problem. These 50 powerful photos prove the Earth still needs our help.

So, what is space junk?

Space junk is just what it sounds like: things that people don’t want or use anymore, just in space. In this case, it’s mostly discarded satellites, related equipment, and bits and pieces of both that have collided and created even more debris. There are approximately 2,000 live satellites currently orbiting the Earth and 3,000 failed ones, and those numbers are growing every year, according to the European Space Agency (ESA). “[Governments, space agencies, and private companies] launch many satellites that we use for phone calls, TV signals, weather satellites, scientific instruments, military satellites, and so on,” says Geoffrey C. Clayton, PhD, a physics and astronomy professor at Louisiana State University. “When these satellites die and stop working, they become space junk.” But that’s not all—space junk is also made up of pieces of the rockets that launched the satellites in the first place, along with bits that have broken off after collisions in orbit.

All of these pieces and bits add up to a staggering number. “There are just under 130 million pieces of space junk in Earth’s orbit,” says Alex Mak, associate director of the University of Toledo Ritter Planetarium. “Of these, about 128 million are smaller than about one centimeter—that’s about the size of a bolt or a screw—and about 35,000 of them are larger than 10 centimeters. The estimated total mass is about 2,000 tons.” And the reason that so much of it is so tiny? “Imagine you launched a satellite on a 12-year mission, turned it off when it completed the mission, and then it eventually collided with something else up there—now it’s in 20,000 little pieces,” Mak explains.

Here are another 24 space facts you never learned in school.

Is space junk dangerous?

Let’s start with the good news: It’s unlikely that space junk would ever be a danger to us here on Earth. “Most space junk burns up in our atmosphere due to friction well before reaching the ground,” says Mak. “There is only a handful of reported incidents of people or property being hurt by space junk.” According to Aerospace.org, a person has less than one in a trillion chance of being harmed.

Now, the not-so-great news. Errant space junk poses a bigger danger to functioning satellites and other spacecraft. There are currently around 29,000 pieces of space debris in orbit that pose “a severe collision risk with satellites and space missions,” according to Universe Today. This is mainly because it isn’t simply floating in space—it’s hurtling forward at thousands of miles per hour, on a potential collision course with one another. “Even a small piece of metal like a bolt coming at the Space Station at thousands of miles an hour would be very dangerous,” Clayton says. Just how dangerous? NASA makes this startling comparison: “Averaging speeds of 22,000 mph, a 1-centimeter paint fleck is capable of inflicting the same damage as a 550-pound object traveling 60 miles per hour on earth. A 10-centimeter projectile would be comparable to 7 kilograms of TNT.”

Depending on the size of the space junk, a collision could shorten a satellite’s life or outright destroy it. That would lead to potential disruptions in service and incredibly costly replacements. Plus, as Mak ironically notes, when space junk damages or destroys satellites, it creates even more space junk and debris, further adding to these problems.

What other kinds of problems could space junk pose?

The main concern is safe space travel. “Some fear that the low Earth orbits (LEOs) may someday become so crowded with space junk as to make it impossible for crewed missions to safely penetrate it on the way to higher orbits or beyond,” says Mak. Keep in mind that the majority of space junk (around 70 percent) is in low Earth orbit, or at less than 1,200 miles above our planet’s surface. Various agencies, including NASA and NORAD, keep track of space junk (and are mostly concerned with the larger bits), by the way, while the Silicon Valley space-mapping company LeoLabs has recently started tracking small debris.

This problem could be exacerbated by something called the Kessler Syndrome. This phenomenon could occur as space junk increasingly collides with other space junk, causing “a runaway chain reaction of collisions and more debris,” according to NASA. At a certain point, the resulting “collision cascading” would render orbits unusable not just in terms of space missions but also for satellites.

Can space junk be cleaned up?

The short answer: Yes. The longer answer is that this isn’t easy. First, there’s already so much out there, and cleanup is a technologically difficult, costly, and dangerous prospect. Mak notes that research is being conducted with approaches such as lasers, space harpoons, and even nets to retrieve or destroy unneeded satellites. In late 2019, the ESA contracted the Swiss company ClearSpace Today to create “the world’s first debris-removing space mission.” Set to launch by 2025, the ClearSpace-1 mission entails having a four-armed robot latch onto space junk, then dive toward Earth’s atmosphere, where would both would burn up, according to CNN.

But cleanup isn’t enough, not over the long haul. There also needs to be a concerted effort to mitigate the creation of more space junk. One way to do this is by thinking ahead in terms of the satellite’s design and ultimate end game. “Some satellites are now launched with a small engine that allows them to alter their orbits after the mission to either burn up or move out of the traffic lanes into what is referred to as a graveyard zone,” says Mak. While the best methods for the disposal of satellites and assorted space junk remain to be seen, one thing is clear: We need to do something to ensure that both space travel and the technology we use on a daily basis stay viable.

Next, check out these NASA discoveries that changed science textbooks.

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Dawn Yanek
Dawn Yanek is a senior editor at RD.com who covers current events, lifestyle, shopping, and entertainment. A former on-air spokesperson and parenting blogger who has appeared on more than 2,500 TV segments, Dawn has likely popped up on your television at some point as an expert or actress. She lives in New York with her husband and their two mind-bogglingly energetic kids.