Space trash, or space junk, refers to human-made debris—pieces of satellites, rockets, and other spacecraft—orbiting Earth. Virtually all of the trash is traveling approximately 28,000 kilometers per hour, posing a significant threat of damaging active spacecraft and satellites.
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Millions of fragments from satellites, rockets, and other spacecraft that are no longer operational move thousands of meters per second as they circle Earth. Even a piece of debris a centimeter in size can cause mission-ending damage to space stations, telescopes, and astronauts.
Although scientists monitor more than 24,000 pieces of large orbital debris, space junk can be as small as a paint fleck. The density of this trash is steadily increasing with the growth of the space industry on Earth.
According to NASA, approximately 9,000 metric tons of debris are orbiting Earth, with 70% of it located in low Earth orbit, where the Hubble Space Telescope and the International Space Station reside. The growing reliance on space-based platforms for modern technologies, including Starlink satellites, increases the risk of debris collisions.
An inactive Russian satellite broke up into nearly 200 pieces, prompting astronauts on the International Space Station to take shelter in a docked spacecraft and a capsule that could be used to escape in case of emergency.
A paper published by NASA scientists Don Kessler and Burton Cour-Palais described a scenario where the density of objects in orbit becomes so high that collisions between them create a cascading effect of runaway debris, preventing future space travel. The risks were confirmed from returned telescope parts showing debris impacts.
In 2023, about 1,500 pieces of space junk fell to Earth, with most consisting of payload fragmentation debris. The vast majority that falls back to Earth burns up before reaching the surface, making it three times less likely to be struck by space trash than by a meteorite.
Although NASA expected the debris to disintegrate after it was jettisoned from the International Space Station in 2024, the flight support component survived reentry. No injuries were reported from the incident.
Despite significant initial costs, a NASA report found that removing small debris would provide savings from preventing mission-ending damage, which would offset expenses within a decade. Financial benefits would also come from using less fuel for maneuvers to avoid collisions with debris.
Active debris removal is likely to focus on larger derelict objects, which are more easily identified and yield better financial returns. One actively researched possibility involves using netting to capture derelict objects before towing them into a controlled descent into an ocean.
As the number of active Starlink satellites increases, greater efforts will be required to keep low Earth orbit free of debris, sparking a new technological space race. NASA has found that using lasers to manage small and medium debris could save up to $9B over 30 years.
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