As the number of satellites in Earth orbit increases, so too does the risk from space debris — and some experts warn certain orbits could already be getting dangerously crowded.
The mass of debris in Earth orbit totals nearly 7 million kilograms, and it ranges from obsolete satellites to tiny flecks of paint.
More than 27,000 pieces of space junk are currently being tracked by the U.S. Department of Defense’s global Space Surveillance Network sensors. Other pieces are too small to detect, but still present dangers to spacecraft due to their high velocities.
Much of the debris will eventually re-enter Earth’s atmosphere and burn up, that process can take years. While it remains in space, it creates new problems and poses risks to space missions and astronauts.
The more collisions there are, the more debris is created, and then that junk can cause even more crashes. The problem can keep compounding. The phenomenon is known as Kessler syndrome, named after retired NASA engineer Don Kessler, who first proposed it mechanisms in 1978.
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At its most extreme, Kessler syndrome may reach a self-perpetuating threshold that could render entire orbits unusable due to debris. According to NASA, some experts believe low Earth orbit is already pushing the limits that could lead to this runaway reaction.
The risks of debris and cascading crashes could continue to rise as companies like SpaceX and Amazon push forward with orbital projects that call for large numbers of satellites.
Amazon's Kuiper internet project, for example, could eventually include more than 3,000 satellites, while SpaceX's Starlink system already has more than 7,000 satellites in orbit and could eventually field more than 30,000.
It some cases, though, new satellites like those used with Starlink are designed to quickly fall into the atmosphere at the end of their useful life instead of lingering in orbits where they could become part of the debris problem.
