Increasing amounts of metal, such as lithium, as a byproduct of the modern-day space race, are beginning to alter the chemical composition of Earth’s atmosphere. 
Robin Wing, and his colleagues at the Leibniz Institute of Atmospheric Physics at the University of Rostock in Germany, measured a 10-fold concentration of lithium atoms in the upper atmosphere around 20 hours after the uncontrolled re-entry of a Falcon 9 rocket.
The findings are detailed in a new studypublished Thursday in Nature.
As spacecraft reenter through the atmosphere, they slowly disintegrate into smaller fragments that burn up and release metals into the upper atmosphere.
Lithium, as well as aluminum and other metals used to construct spacecraft, vaporizes during atmospheric re-entry.
The researchers behind the new study chose to measure lithium because it’s an effective tracer of space debris pollution and is commonly used in spacecraft.
“We discussed several materials, and lithium gave a good compromise of expected signal and challenges in the lidar setup,” Wing said.
“We know that lithium is present in the aerospace-grade lithium-aluminum alloys used in spacecraft construction.”
Although the risks of space debris falling onto the ground are well-studied, there is very little known about the effects of falling spacecraft on Earth’s upper atmosphere.
Using lidar—a laser-based remote sensing instrument used to measure atmospheric conditions—the team of scientists behind the new study detected a sudden increase in the concentration of lithium atoms,
around 10 times the baseline value found in the atmosphere, on February 20, 2025.
This lithium plume stretched from around 58 to 60 miles (94 to 97 kilometers) above sea level.
The researchers observed the plume for 27 minutes until data recording stopped.
They then traced the plume of pollution to the Falcon 9 reentry, linking its area of origin to the uncontrolled path taken by the rocket on its way down.
https://gizmodo.com/study-confirms-reentering-spacex-rockets-are-peppering-the-upper-atmosphere-with-metal-pollution-2000723932