2025 News & Events

Murphy, D.M., M. Abou-Ghanem, D.J. Cziczo, K.D. Froyd, J. Jacquot, M.J. Lawler, C. Maloney, J.M.C. Plane, M.N. Ross, G.P. Schill, and X. Shen, Metals from spacecraft reentry in stratospheric aerosol particles, Proceedings of the National Academy of Sciences, doi:10.1073/pnas.2313374120, 2023.

Abstract

Large increases in the number of low earth orbit satellites are projected in the coming decades [L. Schulz, K.-H. Glassmeier (2021)] with perhaps 50,000 additional satellites in orbit by 2030 [GAO, Large constellations of satellites: Mitigating environmental and other effects (2022)]. When spent rocket bodies and defunct satellites reenter the atmosphere, they produce metal vapors that condense into aerosol particles that descend into the stratosphere. So far, models of spacecraft reentry have focused on understanding the hazard presented by objects that survive to the surface rather than on the fate of the metals that vaporize. Here, we show that metals that vaporized during spacecraft reentries can be clearly measured in stratospheric sulfuric acid particles. Over 20 elements from reentry were detected and were present in ratios consistent with alloys used in spacecraft. The mass of lithium, aluminum, copper, and lead from the reentry of spacecraft was found to exceed the cosmic dust influx of those metals. About 10% of stratospheric sulfuric acid particles larger than 120 nm in diameter contain aluminum and other elements from spacecraft reentry. Planned increases in the number of low earth orbit satellites within the next few decades could cause up to half of stratospheric sulfuric acid particles to contain metals from reentry. The influence of this level of metallic content on the properties of stratospheric aerosol is unknown.

Womack, C.C., W.S. Chace, S. Wang, M. Baasandorj, D.L. Fibiger, A. Franchin, L. Goldberger, C. Harkins, D.S. Jo, B.H. Lee, J.C. Lin, B.C. McDonald, E.E. McDuffie, A.M. Middlebrook, A. Moravek, J.G. Murphy, J.A. Neuman, J.A. Thorton, P.R. Veres, and S.S. Brown, Midlatitude ozone depletion and air quality impacts from industrial halogen emissions in the Great Salt Lake Basin, Environmental Science & Technology, doi:10.1021/acs.est.2c05376, 2023.

Abstract

We report aircraft observations of extreme levels of HCl and the dihalogens Cl₂, Br₂, and BrCl in an industrial plume near the Great Salt Lake, Utah. Complete depletion of O₃ was observed concurrently with halogen enhancements as a direct result of photochemically produced halogen radicals. Observed fluxes for Cl₂, HCl, and NOx agreed with facility-reported emissions inventories. Bromine emissions are not required to be reported in the inventory, but are estimated as 173 Mg year^–1 Br₂ and 949 Mg year^–1 BrCl, representing a major uncounted oxidant source. A zero-dimensional photochemical box model reproduced the observed O3 depletions and demonstrated that bromine radical cycling was principally responsible for the rapid O3 depletion. Inclusion of observed halogen emissions in both the box model and a 3D chemical model showed significant increases in oxidants and particulate matter (PM_2.5) in the populated regions of the Great Salt Lake Basin, where winter PM_2.5 is among the most severe air quality issues in the U.S. The model shows regional PM_2.5 increases of 10%–25% attributable to this single industrial halogen source, demonstrating the impact of underreported industrial bromine emissions on oxidation sources and air quality within a major urban area of the western U.S.