On October 4, 1957, Sputnik I made history as the first satellite to successfully launch into space. But it also marked another milestone: The beginning of space trash.

Space trash or junk is basically any man-made object that exists in space but no longer serves a useful purpose. This includes debris that is released or left behind (like rocket bodies), deactivated satellites that are no longer in use, and even personal items that astronauts accidentally lose—such as a glove, camera or spatula.

“There’s been a pretty steady, exponential rise in the number of objects that space-faring nations have sent into space over the course of the last half century,” says Lisa Ruth Rand, a postdoctoral fellow at the University of Wisconsin-Madison who is writing a book on space trash. “Anytime we launch something into space, for the most part, we’re also generating space junk.”

Image of external fuel tank as it was jettisoned after launch, taken by Discovery's crew. Engineers are using these kinds of images to analyze and understand debris after pieces fell off during the Shuttle's ascent during STS-114. (Credit: NASA)
Image of external fuel tank as it was jettisoned after launch, taken by Discovery’s crew. Engineers are using these kinds of images to analyze and understand debris after pieces fell off during the Shuttle’s ascent during STS-114. (Credit: NASA)

Rand says we don’t know a lot about how this garbage affects space or Earth’s upper atmosphere (for example, in relation to climate change). But we do know that what we’ve left behind has the potential to disrupt people’s lives in two major ways.

The first is that this debris can fall back to Earth. In 1997, a woman was hit in the shoulder by a piece of metal that NASA scientists said was probably a piece of a disintegrating rocket. Though that is the only known instance of space trash hitting a person, there are many other examples of dangerous material that could strike our planet.  In fact, the potential for damage inflicted by no-longer useful equipment is why NASA decided to “kill” the Cassini probe earlier this month, crashing it into Saturn’s atmosphere to prevent it from inflicting damage on that planet’s moons, which studies have shown may be home to living organisms.

An object that crashed through the roof of a home in Freehold Township, N.J.  Geologists ruled out the possibility of it being a meteorite, scientists say it is a stainless steel alloy that does not occur in nature and is most likely "orbital debris", perhaps remnants of a satellite, a rocket or some other spacecraft component. (Credit: Mike Derer/AP Photo)
An object that crashed through the roof of a home in Freehold Township, N.J. Geologists ruled out the possibility of it being a meteorite, scientists say it is a stainless steel alloy that does not occur in nature and is most likely “orbital debris”, perhaps remnants of a satellite, a rocket or some other spacecraft component. (Credit: Mike Derer/AP Photo)

The other is what scientists are more worried about—satellite disruption. That’s because space trash that doesn’t burn up in the Earth’s atmosphere or fall back to our planet gets stuck orbiting around it. There’s a limited amount of orbital room in which we can maneuver satellites, and as space junk continues to take up room, satellites run the risk of crashing into debris (the first time this happened was in 2009).

Although we might not think about it on a daily basis, we use satellites constantly: to make a phone call, plug a destination into a GPS or withdraw money from an ATM. If “space became so full of debris that we could no longer use satellites, it would require reshaping how we do everything,” Rand says. “The military has even said that there’s no way to really operate the way we [do] now without satellites.”

It’s a bit ironic, considering the Air Force first started their research on satellites in the late-1950s because they were concerned about how nuclear war could disrupt Earth-bound communications. They wanted to ensure “that we could keep those lines of communications open, and they wanted to use satellites to do that,” Rand says. Nuclear war is still a threat today, but so is the potential damage debris could inflict before we even realize it. The first clues may only come when the satellites—and the communication systems they power—are already down.

Debris from the space shuttle Columbia streaks across the Texas sky as seen from Dallas. (Credit: Jason Hutchinson/AP/REX/Shutterstock)
Debris from the space shuttle Columbia streaks across the Texas sky as seen from Dallas. (Credit: Jason Hutchinson/AP/REX/Shutterstock)

Rand says that right now we don’t have a way to pull this space trash back to Earth, although experts are looking into it. So the best way to slow its growth is to leave less stuff behind, which private companies like SpaceX are already trying to do, by using reusable rockets that return to Earth.  Eventually, Rand says, some existing space trash will be reabsorbed into the Earth’s atmosphere, thanks to what’s known as the solar cycle. “Solar energy comes out at a pretty regular 11-year cycle—and that energy affects the atmosphere of the Earth in such a way that [it] expands and contracts and can drag things back,” she says. “It’s kind of like a self-cleaning mechanism,” she continues, in that it can remove trash that might otherwise take up valuable real estate. This doesn’t mean the junk “goes away”—some of it dissipates into particles in the upper atmosphere, and some of it falls to Earth—but it does ease the threat the trash poses to satellites.

As helpful as these natural cycles are, they can only take care of so much. In 2011, the National Research Council released a study saying that we had already reached a space junk “tipping point”—and that if we don’t try to get a handle on the problem now, we won’t be able stop it from becoming an ever-worsening crisis.