Above Earth, what orbits is not only working hardware, but everything left behind. Space debris is any human-made object in orbit that no longer serves a useful purpose: spent rocket stages, dead satellites, lens caps, bolts, and fragments from explosions and collisions. Even a centimeter-sized piece is dangerous to an operational spacecraft. In low Earth orbit, relative speeds reach 7–15 km/s, so an impact is often compared to an explosion. How much is there According to the European Space Agency (MASTER-8 model, early 2026 population, statistics updated to 31 July 2026), Earth orbit holds roughly: 68,450 objects larger than 10 cm (only about 11,300 of them active payloads); 1.5 million fragments between 1 and 10 cm; 230 million particles from 1 mm to 1 cm. Surveillance networks regularly catalogue about 47,000 objects. The total mass of everything humans have left in orbit exceeds 17,000 tonnes. Since 1957 there have been about 7,320 successful launches, placing roughly 27,500 satellites into orbit; about 18,850 of those are still in space, and about 15,900 are still functioning. NASA’s catalogue (as of 4 August 2026) lists 34,054 tracked artificial objects: 19,154 spacecraft and 14,900 rocket stages, structural pieces, and debris. The United States accounts for the largest share (18,323), followed by Russia (6,575) and China (5,737). Differences between agency figures come from different detection thresholds, models, and definitions of what counts as catalogued. Most debris is in low Earth orbit (LEO), especially in the bands used by large constellations. Objects in geostationary orbit are fewer, but they stay far longer: without a maneuver they can remain for decades or centuries. Where it comes from The main sources are not only old spacecraft. More than 660 fragmentation events have been recorded: explosions of residual propellant in stages, battery ruptures, deliberate anti-satellite tests (China in 2007, Russia in 2021), and collisions. The best-known collision is the 2009 impact between Cosmos-2251 and Iridium 33. A newer driver is mass launches. In ESA’s 2026 Space Environment Report, 2025 saw more than 300 launches and more than 4,000 new payloads placed in orbit. On average about ten objects are launched each day, while more than three intact satellites or rocket bodies reenter the atmosphere. Not enough satellites leave congested orbits quickly enough at the end of their missions. Why it matters Small debris is rarely tracked individually, yet it can disable a satellite. Operators already perform avoidance maneuvers routinely: for the ISS and large constellations this is normal operations, not an exception. The long-term threat is the Kessler syndrome: a chain reaction in which collisions create fragments that cause further collisions. ESA concludes that even if launches stopped completely, the number of objects in low Earth orbit could keep rising because of fragments already there. The 2026 report notes that signs of this self-sustaining growth are appearing earlier than in previous forecasts. A long-term environmental load index rose in one year from about 4 to about 50 relative to a threshold considered acceptable in a 2014 reference scenario. ESA says active debris removal is needed to stop that growth. There are ground effects as well. Debris is reentering more often. The risk of casualties on the surface from falling stages and satellites is still small per person, according to ESA, but the global annual risk is rising with the number of reentries. Burning spacecraft also add metals to the upper atmosphere. The contribution is still smaller than the natural meteoroid influx, but for some metals it is already noticeable. What is being done Responses fall into prevention and cleanup. Prevention means passivating rocket stages (venting leftover fuel and pressure so they do not explode) and removing satellites from working orbits at end of life—by atmospheric drag in low orbit, or by moving them to a graveyard orbit in geostationary space. IADC guidelines and operator requirements are tightening: ESA has cut its own target for clearing low Earth orbit to five years. Large constellations are designed for controlled reentry. Cleanup is only beginning. Harpoons, nets, magnetic captures, robotic arms, and tugs that drag a large object out of orbit have been tested. These are demonstrations, not an industrial service: docking with a non-cooperative, tumbling object is expensive and difficult, and legal questions—who owns the debris, and who may touch it—are unresolved. Tracking is also improving, through radars, optical telescopes, and commercial catalogues. Better orbits mean fewer false alarms and safer maneuvers. Orbit is a shared and finite resource. As long as launches grow faster than the share of spacecraft that reliably leave working altitudes, debris density will increase. The problem can be contained technically: fewer explosions, mandatory disposal, and active removal of the most dangerous large objects. Without that, some bands of low Earth orbit risk becoming too costly and too hazardous for routine use.