Metals from space debris found in stratosphere

When space debris reenters the atmosphere, the heat generated from friction causes most of it to vaporize. Recently, scientists have found that the vaporized metals condense as they descend, ending up in aerosol particles in the stratosphere. (Proc. Natl. Acad. Sci. U.S.A. 2023, DOI: 10.1073/pnas.2313374120).

This discovery is part of the Stratospheric Aerosol processes, Budget and Radiative Effects (SABRE) mission. During a series of flights in February and March 2023 the researchers sampled the stratosphere at altitudes up to 19 km. The researchers detected almost two dozen elements that come from meteors, volcanoes, and vaporized spacecraft.

Meteors are considered the main sources of sodium, magnesium, chromium, iron, and nickel, but the researchers also found aluminum, copper, lead, and lithium that could not be accounted for by natural causes. “What we measured is consistent with what we know about what spacecraft are made of,” says Daniel Murphy, an aerosols researcher and one of the study authors. The team found exotic metals, like niobium, silver, lithium, and copper, that are virtually absent in meteors, but can be accounted for by space debris.

No larger impacts on the stratosphere have been observed yet. But with space launches set to skyrocket, debris has the potential to change the chemistry going on within the stratosphere, Murphy says. “We don’t really know what the effects are going to be. For me, that’s uncomfortable.”

Murphy and his team are looking to make more measurements in different parts of the Earth’s atmosphere, including over the tropics and southern hemisphere. They hope to provide data that would help other scientists study the potential of changes in stratospheric chemistry, and what the long-term effects may be.