Origins of stratospheric particles through an updated automated classification: revisiting the 1981-2020 period of the NASA Cosmic Dust Collections

Every year, from 2000 to 8000 tons of natural extraterrestrial meteoroids are ablated in our atmosphere in the form of aerosols, estimated as a fraction of the total mass of incoming meteoroids. In 2019, the corresponding number for anthropogenic materials was estimated at about 263 tons, originating from launches and re-entries of rocket bodies, satellites, and space debris [1]. These injections of anthropogenic materials raise concerns about their effects on the Earth’s atmosphere such as ozone depletion, radiative forcing  and other unknow effects [2], [3], [4]. Furthermore, the anthropogenic injections are expected to increase significantly due to the rapid increase in launch rates and number of mega-constellations planned for the coming years. Indeed, there have been more satellites launched in the last 6 years than between 1957 and 2018 [5] and these numbers are set to grow, especially in the low Earth orbit region located below 2000 km [6].

However, large uncertainties remain about the evolution of the proportion and origins of these injected anthropogenic particles. This work attempts to reduce these uncertainties by further exploring the compositions of stratospheric particles collected in situ by the NASA Cosmic Dust program over 40 years.

Since 1981, the NASA Johnson Space Center (JSC) has been collecting dust particles from the lower stratosphere with airborne collectors during specific campaigns and published ~5500 preliminary analyses in the “Cosmic Dust Catalogs”. Each preliminary analysis is based on Scanning Electron Microscopy (SEM) images, some morphological characteristics and X-ray Energy-Dispersive Spectrometry (EDS) composition. The particles are then classified into four main groups: Cosmic, Terrestrial Contaminant Natural, Terrestrial Contaminant Artificial and Aluminum Oxide Sphere. Nevertheless, at least 20% of them remain ambiguously classified. The recent digitalization of all the published catalogs gives us the opportunity to explore their composition using multivariate analysis techniques such as Principal Component Analysis, and automatic clustering of the EDS spectra for classification. Nonlinear projected maps of the EDS composition can help visualize the classification of the particles [7]. The compositional clusters obtained can be used to identify the origin of each particle and constrain the atmospheric injection of each material. The temporal variations of the different compositions injected will be assessed and additional EDS data taken on meteorites and natural minerals will be included in the analysis to define natural material references.

In the future, this work will be complemented with new EDS spectra, SEM images and Raman spectroscopy of selected old samples and post-2020 collected samples curated at NASA JSC in Houston.

 

[1] Schulz and Glassmeier, Advances in Space Research, 2021. DOI: 10.1016/j.asr.2020.10.036

[2] Ferreira et al., Geophysical Research Letters, 2024. DOI: 10.1029/2024GL109280

[3] Jones et al., Journal of Geophysical Research, 1995. DOI: 10.1029/95JD01539

[4] Ross and Sheaffer, Earth’s Future, 2014. DOI: 10.1002/2013EF000160

[5] McDowell, « Jonathan’s Space Report », Accessed: Jan. 2025. https://planet4589.org/space/log/launch.html

[6] Gaston et al., Frontiers in Ecology and the Environment, 2023. DOI: 10.1002/fee.2624

[7] Lasue et al., Meteoritics & Planetary Science, 2010. DOI: 10.1111/j.1945-5100.2010.01059.x