Space debris: what are the chances of humans being harmed by satellite fragments falling to Earth?

A fiery streak in the sky, a burning metal fragment falling to the ground—such scenes instill fear in people that one day space debris could strike an unsuspecting victim. With thousands of satellites orbiting Earth and even more being launched each year, it may seem that a piece of space junk hitting someone is just a matter of time. The reality of this danger is discussed by BBC Science Focus.

Although particles of space debris sometimes return to Earth, the vast majority burn up in the atmosphere before reaching the ground. Even large objects, such as spent rocket stages, rarely cause harm to people or structures, although there have been instances of such incidents occurring recently happened.

Over the past 50 years, NASA has recorded an average of one piece of space debris falling to Earth each day, but there have been no confirmed cases of fatalities or serious injuries resulting from these incidents.

In comparison, aviation accidents occur much more frequently. On average, there are at least three aviation accidents every day, mostly involving small non-commercial aircraft. Despite this, fatal accidents due to plane crashes remain relatively rare, and the likelihood of encountering space debris is even lower.

Unlike an airplane, which typically remains intact until impact and may carry fuel, space debris usually consists of small, lightweight fragments, such as shards or pieces of carbon fiber panels. The height from which debris falls does not significantly affect the damage it can cause. Objects falling from a height of 300 km reach their terminal velocity long before impact, making them no more dangerous than debris falling from a height of 10 km.

Furthermore, while airplanes are concentrated over populated areas, space debris is scattered randomly across the planet. If the entire population of Earth were evenly distributed, it would cover only 0.0002 percent of the Earth's surface, meaning that even if every piece of space debris were deadly, it would still miss in 99.9998 percent of cases.

This brings us to the conclusion that statistically, one person has a chance of dying from such an incident every 1,300 years. In the long run, even the threat of a planetary collision with asteroids, though minimal, is still higher than the risk from falling space debris. NASA's Center for Near Earth Object Studies (CNEOS) actively monitors thousands of asteroids to assess potential risks. Although collisions with large bodies are extremely rare, ongoing research allows for the early identification of any potential threats to our planet.