Evolution of the population of stratospheric aerosols on the 1981-2010 period: focus on injections related to space activities during launch and re-entry of satellites.

Space traffic is increasing rapidly, with a threefold increase in launches and a thirtyfold increase in satellites launched between 2000 and 2024 (Taupin et al., 2025). In 2024, we estimate that the ratio between the re-entered dry-mass from anthropogenic space activities (DISCOSWeb, J.McDowell RCAT) and natural input from Earth’s cosmic natural input (Carrillo-Sánchez et al., 2020) is between 20-40%. For aluminum in particular, this ratio was estimated to exceed 100% in 2024 (Ferreira et al., 2025). In addition, the space traffic increase is mainly occurring below 600 km altitude, where satellites naturally decay in less than ~10 years. This mass is ablated in the form of atoms and solid aerosols that accumulate in the stratosphere. They may impact radiative forcing and ozone depletion, and have other unknown effects at local, regional and global scales (Ferreira et al., 2024, Ross et al., 2014). It is therefore important to accurately quantify the past and present levels of these injections in order to model their atmospheric effects.

First, we present a finely tuned classification that helps to assess the potential origin of solid stratospheric aerosols (~1-100 microns diameter) collected in-situ by aircrafts mostly over the United States by NASA's Cosmic Dust program between 1981 and 2020. Here we study the 1981-2010 period comprising more than 4 400 particles. Based on the Energy Dispersive X-ray spectra of these particles and previous work (Lasue et al., 2010), we have developed a semi-automated method that classifies them into compositional clusters. For example, we identified potential artificial contaminants rich in Al, Cd, Cu and Ti that stand out from other clusters. For clarity, the particle compositions are compared to known minerals and pure elements. A visualization of the classification will be presented for each year in which particles were sampled, showing the evolution of the aerosol population composition.

Soon, this work will be supplemented by a new spectral analysis of 46 particles that will serve as a calibration to improve the quantification of the chemical composition of all particles in the catalogues.

Secondly, we will introduce a new method for estimating the re-entered ablated mass from space waste. Existing methods rely on average ablation coefficients (Schulz et al., 2021) or focus on specific chemical species (Ferreira et al., 2025).  We use the DEBRISK software (from CNES) to estimate several average ablation profiles for a few simplified models of satellites and rocket upper stages based on their different average cross-sections, masses, and orbital parameters. Then, we use these parameters available in DISCOSweb to derive the total ablated mass of satellites and rocket upper stages in the stratosphere from 1981 to 2010. Finally, we estimate the total mass of black-carbon and alumina injected in the stratosphere during all orbital launch on the same period, using a newly created database on propellant masses cross-referencing information from different sources (DISCOSweb, J.McDowell GCAT, user manuals). These numbers will then be compared to the evolution of the solid aerosol population presented in the first part.