Space waste: An update of the anthropogenic matter injection into Earth’s atmosphere

Abstract

Large satellite constellations are one of the main reasons for an increasing amount of mass being brought into low Earth orbit in recent years. After end of life, the satellites, as well as rocket stages, reenter Earth’s atmosphere. This space waste burns up in the atmosphere and thus injects a substantial amount of its matter into the mesosphere and lower thermosphere. A first comprehensive analysis of the anthropogenic injection and a comparison to the natural injection by meteoroids was presented by Schulz and Glassmeier (2021) (Advances in Space Research, 67 (3), 1002-1025). They found significant and even the dominant injection of several metal elements regularly used in spacecraft compared to the natural injection. The first observations of space waste remnants in stratospheric aerosol particles (Murphy et al., 2023, PNAS, Vol. 120, No. 43, e2313374120) confirmed several of these estimates, but also revealed differences and new insights: in particular, a much more extensive range of elements. These inventories and observations raise questions of possible environmental effects, especially on the stratospheric ozone layer (Mitchell et al., 2024, Understanding the Atmospheric Effects from Spacecraft Re-entry, ESA, Whitepaper, 2024). The current study presents an update to the space waste injection estimates of Schulz and Glassmeier (2021), assessing the years from 2015 to 2025 using available reentry databases but also considering future mass influx scenarios. Combining mass influx data with detailed estimates of average satellite and rocket stage composition as well as ablation factors allows the estimation of the mass injection of 43 elements and thus a much more detailed comparison to the meteoric injection. Comparison of estimated elemental fluxes to stratospheric aerosol data shows excellent agreement. In general, from 2020 onward, a strong rise in space waste mass influx to the atmosphere can be seen, which has led to more than double the atmospheric injected mass in 2024 compared to levels from 2015 to 2020. Future scenarios discussed by Schulz and Glassmeier (2021) may already be reached by the end of 2025. In 2024, 24 elements were dominating the meteoric injection compared to 18 in 2015, this might increase to 30 in the future. Several of them are transition metals, which are known for their catalytic activity. This indicates a substantial risk of long-term adverse effects on the atmosphere such as ozone depletion, radiative effects and changes in cloud formation, if no action is taken. Research is urgently needed into the atmospheric accumulation, chemistry, and general atmospheric effects of specific elements.