New research suggests that the proliferation of megasatellite constellations may be contributing to atmospheric pollution beyond the already concerning issue of space debris. The study highlights the potential damage to the Earth's atmosphere from reentering spacecraft and rocket stages, as well as the increased risk of space waste impacting the planet.
According to a preprint study on ArXiv, reentering spacecraft inject significant amounts of material into the mesosphere and lower thermosphere, potentially weakening the Earth's ozone layer. While awaiting peer review, this research adds to a growing body of academic inquiry into the environmental effects of increased space activity. The study differentiates between “space waste,” defined as incoming human-made material and its effects on Earth’s atmosphere, and orbiting space debris.
The research, led by scientists from Technische Universität Braunschweig, indicates that reentering "transition metals" such as titanium and copper – commonly used in spacecraft and rocket stages – may trigger “long-term adverse effects on the atmosphere such as ozone depletion, radiative effects and changes in cloud formation, if no action is taken.” The paper also notes the use of stainless steels and aluminum in space hardware, with the scientists suggesting further study into the potential impact of aluminum.
Leonard Schulz, a researcher at Technische Universität Braunschweig, emphasized the need to understand the scale of the problem, including identifying space waste that survives reentry and impacts Earth. “The increase in material being injected into Earth’s atmosphere is really unprecedented,” Schulz told SpaceNews. “We now see the first effects of a new era in space activities, the era of large satellite constellations. Research has to really focus on the possible effects these substances can have on the ozone layer,” he said.
Schulz noted that the associated risks are substantial, despite the need for further investigation. The research indicates that the influx of "space waste" has more than doubled between 2020 and 2024, primarily driven by materials from spacecraft. The environmental impact of reentering spacecraft is now surpassing that of meteorites. “This shows that the onset of the large satellite constellation age is the driving factor of the increased space waste reentry into the atmosphere,” the paper states. “Allowing this uncontrolled experiment on our atmosphere to continue is inadvisable,” Schulz said. “We should work to decrease the mass input into the atmosphere now, while retaining the ability to continue the utilization and exploration of space.
Schulz advocates for collaboration between scientists and industry to achieve these goals, stating “One first step is to share data, for example on the composition of spacecraft. While some members of industry have helped us immensely by sharing such data, many are not willing to do so.”
Schulz also participated in a separate study, led by Robin Wing of the Leibniz Institute of Atmospheric Physics, examining the uncontrolled reentry of a SpaceX Falcon 9 upper stage. This study focused on the pollution resulting from the reentry, tracing a plume of lithium vapor after the stage disintegrated over Central Europe. The researchers found “strong evidence” linking the lithium plume to the Falcon 9 event, supporting concerns that space traffic may pollute the upper atmosphere. “This finding supports growing concerns that space traffic may pollute the upper atmosphere in ways not yet fully understood,” Wing and his coauthors concluded in the paper. “Continued growth in satellite launches and re-entries may lead to cumulative effects, with implications for long-term atmospheric composition and climate interactions.”
Wing's team is currently developing a new multi-metal space debris lidar system to track various elements in the mesosphere. “We hope that by making long-term observations of lithium/sodium ratios that we can determine how much of an impact reentering space debris has on the atmosphere.” The lidar will also allow for systematic study of other metals, including copper, titanium, and aluminum, potentially linked to the space industry.
Wing acknowledged the difficulty in definitively assessing the planet's implications: “Simply put, we don’t know enough yet. Much more research is needed. However, I would say that there is a realistic concern for the chemistry of the middle atmosphere,” Wing said, “particularly the ozone layer, with the introduction of so many materials and elements which are not naturally occurring in the atmosphere.” He also highlighted the impact of rocket exhaust on the atmosphere. “The injection of water vapor, fuel, debris and other elements associated with rocket launches could become a significant concern if current launch trends continue,” Wing said.