What is space debris?

Where it comes from

NASA's Orbital Debris Program Office counts as debris anything people have put in orbit around Earth that has stopped doing a useful job.

Explosions and collisions are the main source of large debris, NASA says. Two events account for about one-third of all cataloged debris. They were China's intentional destruction of its Fengyun-1C weather satellite in 2007 and the accidental 2009 collision of the Iridium-33 and Cosmos-2251 satellites.

Altitude decides how long debris lasts. Below 600 km it normally falls back to Earth within several years, NASA says. At 800 km orbital decay often takes centuries, and above 1,000 km a thousand years or more.

Why it matters

Debris in low Earth orbit travels at 7 to 8 km per second. NASA puts the average impact speed at about 10 km per second. So even a small fragment hits with a lot of energy.

Only objects larger than 10 cm are tracked routinely, NASA says. The European Space Agency (ESA) listed about 47,140 objects in surveillance catalogs as of July 31, 2026. It estimated that more than 660 break-ups, explosions, collisions or similar events have produced fragments.

Estimates of smaller pieces differ. NASA's undated FAQ cites roughly 500,000 objects between 1 and 10 cm. ESA's statistical model, using a February 2026 reference population, puts the number at 1.5 million.

ESA's overview of its 2026 Space Environment Report describes the greatest long-term threat as the Kessler syndrome, a self-sustaining chain in which collision debris causes further collisions.

Where things stand in 2026

No international treaty covers orbital debris, NASA notes. Space agencies and a United Nations committee have published mitigation guidelines instead. On September 29, 2022, the U.S. Federal Communications Commission adopted a rule requiring satellites in low Earth orbit to deorbit no later than five years after their missions end. It replaced a 25-year guideline.

The ESA overview, published September 14, 2026 and based on data through 2025, counted more than 300 launches and over 4,000 new payloads in 2025. It said that:

• too few satellites leave congested orbits at the end of their lives
• debris would keep increasing even with no further launches
• active debris removal is required

ESA's Space Environment Health Index measures strain on the orbital environment against a sustainable benchmark. ESA said it rose from about 4 to 50 in one year.