Since the dawn of the space era, exploring beyond Earth, humans also started disposing of waste in orbit. By the late 1950s, what began as a few discarded items has evolved into a floating scrap yard around our planet in the 21st century, a concern highlighted by Josef Aschbacher, the director of the European Space Agency (ESA).
Space junk refers to debris of various sizes left by human activity, hurtling around Earth at incredibly high speeds. Old rocket stages, abandoned satellites, and even discarded missile parts pose real threats not only to astronauts aboard missions but to the broader future of military, civil, and commercial communications and space exploration as a whole. These millions of tiny projectiles travel at about seven kilometers per second, making every collision a potential setback for ongoing and future programs.
The International Space Station, the heaviest and most complex object in low Earth orbit, has been used as a scientific laboratory by nations around the world. It has repeatedly needed protection from debris impacts and has performed more than twenty avoidance maneuvers since 1999. The most recent unscheduled orbit correction occurred in July 2020.
thousands of pieces
ESA tracks approximately 26,000 objects from Earth, but only about 2,800 are functioning satellites or have some defined role. The majority are fragments resulting from collisions and breakups in space.
In total, about 5,000 objects exceed 1 meter in size, 25,000 are larger than 10 centimeters, 750,000 measure between 1 and 2 centimeters, and an astonishing 166 million particles exceed 1 millimeter in diameter.
Projections from ESA indicate a 5 percent yearly increase in orbital junk, with expectations that it could triple over the next two decades.
The concern worsens for experts at the United Nations and among astrophysicists: debris in orbit continues to collide with other pieces, generating more debris even if new objects stop being launched. This scenario is often described as the Kessler syndrome, a concept proposed in 1978 by a NASA expert who warned of a cascade of collisions that could render certain orbital regions unusable.
Most fragments cluster in the most valuable altitude bands — low Earth orbit from roughly 200 to 2,000 kilometers above the planet, and geostationary orbit around 36,000 kilometers up, which serves as a critical artery for communications satellites.
Today, the atmosphere still acts as a cleaning agent, gradually slowing and reentering smaller debris and those in lower orbits, though this natural process does not remove all risks.
At the European Space Debris Conference in 2021, findings underscored that removing defunct objects from space is part of the solution. Luisa Innocenti, leader of ESA’s cleanup initiative, acknowledged the challenge but suggested that future satellites should be designed for easier retrieval, which could significantly reduce risk.
ESA: a difficult mission
ESA has been pursuing a dedicated mission to capture and remove orbital waste. The project, named for a Swiss company that developed the capture device, ClearSpace, aims to launch in 2025 to recover a 100-pound piece of a Vega rocket from 2013, presently orbiting at around 660 kilometers altitude. The plan is to bring the captured item into a lower orbit where atmospheric drag will cause it to burn up upon reentry.
In the longer term, a follow-up approach would see the hunter satellite guiding scrap toward Earth, allowing it to disintegrate as it reenters the atmosphere. This technology remains under development and testing due to the complexity involved. There is currently no universal international regulation on space debris, leaving governance primarily in the hands of participating states and private entities.
Yet attention to the problem is growing. Researchers project a possible future where Earth is ringed not by ice and rock, but by orbital junk, a grim reminder that the planet’s orbital environment must be safeguarded for sustainable exploration and use.
Noting the stakes, some voices appeal for a broader sense of responsibility. Thomas Schildknecht, director of the International Astronomical Union, speaks of a right to a clear sky — a lifelong heritage of humanity. He argues that safeguarding this view is essential for understanding the universe and our origins, a point he raised at the European Conference on Space Debris.
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The environmental sector continues to seek better policies and practices to keep Earth’s orbit clear, with ongoing discussions about how space activities should be regulated and managed to minimize future debris creation.