Rocket launches may be contributing to pollution in Earth’s upper atmosphere, with potentially unknown consequences for the ozone layer. On February 18, 2025, SpaceX launched a Falcon 9 rocket for the 438th time, sending approximately 20 Starlink satellites into low Earth orbit, as reported by Space.com.
The company celebrated the first stage of the rocket returning for a landing in the Bahamas. Though, on February 19, residents of Poland reported falling debris from the second stage of the SpaceX rocket, and the Polish space agency POLSA confirmed “that during the night of February 19, 2025, between 04:46 and 04:48, an uncontrolled reentry into the atmosphere above Polish territory of a Falcon 9 R/B carrier rocket stage took place.”
Detection Over Northern Germany
The uncontrolled reentry of the Falcon 9’s second stage had unforeseen consequences. Researchers at the Leibniz Institute of Atmospheric Physics have published a scientific article, approximately one year later, detailing the detection and measurement of a lithium cloud in the upper atmosphere over western Ireland, extending as far north as Germany at an altitude of 96 kilometers.
The team initially detected a tenfold increase in lithium atoms above the German town of Kühlungsborn, using a lidar system – a laser-based remote sensing technology that also estimates the distance to detected particles – “approximately 20 hours after the uncontrolled reentry of a Falcon 9 upper stage.”
“The maximum density of the lithium layer was less than 3 atoms cm⁻³ for most of the measurement. A sudden increase in the signal by a factor of 10 was detected just after midnight UTC on February 20,” they explained.
Researchers then ran simulations to determine the source of the atoms. “The entire set of calculated trajectories (in blue) is shown in Figure 3 [below] with a heat map of probability density indicating the region above the United Kingdom and Ireland where the lithium plume likely originated.”
On the map, the black line represents the reentry trajectory of the Falcon 9, and the curve composed of modest circles represents an example of a possible trajectory they simulated, corresponding to the time the rocket entered the upper atmosphere.
Lithium as a Signature of Space Debris
Researchers explain that lithium was chosen as the target metal “to detect signatures of space debris due to its presence in minute quantities in chondritic meteoroids and its well-documented applications in spacecraft, including lithium-ion batteries and lithium-aluminum alloy (Li-Al) shell coatings.”
Their work demonstrates that lidars, particularly those using resonance fluorescence, can be used to detect lithium in the upper atmosphere “when combined with other atmospheric measurements and supported by modeled analysis.” This research aims to better understand what is happening before materials enter the ozone layer, as previous studies have shown that satellite combustion could seriously damage the ozone layer. However, detecting and quantifying pollutants in the stratospheric ozone layer is complex and expensive, according to the researchers.
The authors also emphasize that their work “supports growing concerns that space traffic could pollute the upper atmosphere in ways that are not yet fully understood. The continued growth of launches and satellite reentries could lead to cumulative effects, with implications for long-term atmospheric composition and climate interactions.” The consequences of this pollution, both on the upper atmosphere and the ozone layer, remain unknown.
It’s worth noting that SpaceX launches are responsible for other forms of pollution. In January 2025, debris from Starship fell on beaches and roads in the Turks and Caicos Islands. For several years, astrophysicists have warned about the threat posed by satellite constellations to astronomical observations, a threat that has accelerated with the size of these constellations. The increasing frequency of launches underscores the need for a deeper understanding of their environmental impact.
