Rising Space Waste

Leonard Schulz, Technische Universität Braunschweig, Germany, and colleagues have studied how reentering satellites and rocket stages—particularly from large satellite constellations—inject material into Earth’s atmosphere, updating prior estimates of space waste from 2015–2025 and projecting future scenarios. To reduce collision risks in orbit, defunct satellites and rocket stages are intentionally burned up in the atmosphere, where they release a diverse mix of elements—including aluminum, lithium, fluorine, chlorine, and bromine—from their structural and functional materials. It is unclear how this material might be changing atmospheric chemistry.

The researchers combined reentry databases, detailed knowledge of satellite and rocket compositions, and ablation factors to calculate the mass injection of 43 elements, comparing it to natural meteoroid input. The goal was to assess the scale of anthropogenic metal deposition in the mesosphere and stratosphere, identify potential environmental effects (e.g., ozone depletion, radiative forcing, cloud formation), and highlight the need for further research on atmospheric accumulation and chemistry of these elements.

The team found that human space activities are now a significant source of upper-atmosphere metals, with potentially wide-ranging environmental consequences.

The Earth’s atmosphere is constantly bombarded by meteoroids, which deposit around 12,300 tons of material annually. Added to this is around 900 tons of space debris for 2024. In comparison, this is relatively small, but the amount of metals added is considerable. Reentering satellites and rocket stages now contribute more of certain metals (e.g., Al, Cu, Li, Pb) to the mesosphere and lower thermosphere than natural meteoroid ablation.

From 2020 onward, space waste entering the atmosphere has risen sharply, with the total injected mass in 2024 more than double that of 2015–2020, driven largely by large satellite constellations. In 2024, 24 elements dominated the anthropogenic injection compared to 18 in 2015, potentially reaching 30 in the near future, including many transition metals with catalytic activity.

According to the researchers, the estimated elemental fluxes align well with measurements of stratospheric aerosol particles, validating the modeling approach. The presence of these metals raises concerns for ozone depletion, changes in cloud formation, radiative effects, and long-term atmospheric chemistry.