Atmospheric pollution from space junk could be a huge problem

A SpaceX rocket that burned up after re-entering the atmosphere released a plume of vaporized metals over Europe, a type of pollution expected to increase as spacecraft and satellites proliferate.

Designed to dive into the Pacific Ocean for possible reuse, the Falcon 9’s upper stage lost control due to engine failure and fell out of orbit over the North Atlantic in February 2025.

People across Europe saw hot debris streaming across the sky, some of which crashed behind a warehouse in Poland. see news, Robin Wing at the Leibniz Institute of Atmospheric Physics in Germany and his colleagues turned on lidar, an instrument for sensing the atmosphere. Twenty hours later, he detected a tenfold increase in the content of lithium, a key component of rocket hulls, in the upper atmosphere as a cloud of vaporized metal rolled overhead.

Atmospheric modeling indicated that this plume drifted 1,600 kilometers from the area where Falcon 9 re-entered the atmosphere. The study is the first to trace pollution from high altitudes to a specific spacecraft reentry.

The tiny metal particles “can catalyze ozone destruction, create clouds in the stratosphere and mesosphere, and affect the way sunlight passes through the atmosphere,” says Wing. “But all of this is understudied.

Concerns about this type of pollution are growing as commercial space launches skyrocket and companies expand their mega-constellations of satellites, such as SpaceX’s Starlink and Amazon’s Leo. There are already about 14,500 satellites in orbit, and last month SpaceX requested the launch of 1 million more for Elon Musk’s goal of creating orbital data centers for artificial intelligence.

To avoid an uncontrollable cycle of collisions that produce more and more space debris, satellites are usually allowed to crash and burn up at the end of their lives. Experts say the amount of space debris particles could increase 50-fold in the next decade, surpassing 40 percent of the mass currently brought into the atmosphere by meteoroids.

There’s a misconception that space junk burns up in the atmosphere and disappears, he says Daniel Cziczo at Purdue University in Indiana, who was not involved in the study. “Here we’re going to hit the brakes and do a really thorough analysis of what effect this material could have.”

The Falcon 9 plume contained an estimated 30 kilograms of lithium. But due to the composition of the alloys in the rocket hulls, it would contain a much larger amount of aluminum.

Vaporized aluminum reacts with atmospheric oxygen to form alumina particles that provide a surface where chlorine compounds can more easily decompose. Chlorine radicals released by this process react with ozone molecules in the stratosphere and destroy them.

Researchers estimate that the spacecraft’s burnout is release 1000 tons of aluminum oxide into the atmosphere every year and growing. This threatens to widen the ozone hole in the Southern Hemisphere, which is shrinking as countries phase out ozone-depleting cooling gases. Ozone loss could let in more of the sun’s ultraviolet rays, which cause skin cancer.

“When it comes to metals, we’re kind of moving into this new paradigm where the upper atmosphere is more and more affected by anthropogenic pollution than by natural sources,” he says. Eloise Marais at University College London. “Space debris is starting to disrupt progress with the ozone hole.”

Metal oxide particles can also serve as nuclei on which water vapor can condense into droplets, forming cirrus in the upper troposphere, which tend to trap heat.

Scientists have measured particles from burned spacecraft in cirrus clouds. If they promote cirrus formation, this could exacerbate global warming, although this impact would still be small compared to that of greenhouse gases such as carbon dioxide.

“There is a lot of scientific evidence that this material could have harmful effects on our atmosphere, and now it’s up to us as scientists to find out if those effects are happening and how bad they are,” says Cziczo.

There may be solutions such as building satellites out of materials like wood – although this could still release black carbon soot upon re-entry – or moving more of them into high-altitude “graveyard orbits”.

“Before we do that, we have to take some time and think about what we’re doing,” says Wing. “The explosion of the satellites… is very fast and we don’t know the consequences.

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