Space debris

Space debris, also known as space junk or cosmic debris, refers to old, non-working human-made objects floating in space, mostly around Earth. These include broken or abandoned satellites, pieces left over from old rockets, and tiny fragments created when objects crash or break apart. Even small bits, like paint flakes or bits of rock, can cause problems because they move very fast.

These pieces of space debris can damage satellites, space stations, and other spacecraft. For example, the International Space Station has special shields to protect it from tiny bits flying by. Sometimes, bigger pieces are so risky that the space station has to move out of the way to avoid a crash.

There are a lot of these pieces floating around. As of April 2025, there were over 40,000 objects big enough for people on Earth to track. But there are also millions of smaller pieces that we can’t track, and they can still hurt satellites and other spacecraft. Scientists and space agencies are working on ways to track these pieces and maybe even clean some of them up, because space debris is a big problem for anything that travels into space.

History

Space debris started building up in Earth's orbit when the first artificial satellite, Sputnik 1, was launched in October 1957. Before that, natural pieces from Earth could have already been in space. After Sputnik, groups like the North American Aerospace Defense Command (NORAD) began tracking all objects in space, such as satellites and parts of rockets.

Over time, more pieces of debris appeared because of explosions in space, sometimes from old rocket parts breaking apart. As technology improved, scientists could better track these pieces. Today, many pieces of space debris remain in orbit, and efforts are being made to understand and manage this growing problem.

Characterization

As of January 2019, there were over 128 million tiny pieces of space debris smaller than a centimeter, and about 900,000 pieces between 1 and 10 centimeters in size. There were also around 34,000 larger pieces, each at least 10 centimeters across.

Low Earth Orbit (LEO), the area of space closest to Earth, holds most of the space debris—about 85%. Many satellites orbit here, and they pass each other often, which can lead to collisions. When two satellites collide, they create even more debris, making it risky for other satellites. Scientists worry that too many collisions could make some parts of LEO too dangerous for satellites to use.