Laboratory Research on the Atmospheric Impact of Spacecraft Re-entry Debris: Perspectives and Future Challenges

The rapid growth of space debris, especially in Low Earth Orbit (LEO), poses a rising risk to both space operations and Earth's atmosphere.  Debris fragments, even minuscule in size, can cause significant damage due to their high orbital speeds. To mitigate risks, controlled re-entry of debris is common practice, but this introduces a new concern: the increasing mass of human-made materials injected into the atmosphere. As satellites and rocket bodies disintegrate, they release substantial quantities of metals, altering the composition of the stratospheric aerosol. The effects of these new materials within the stratospheric aerosol are still uncertain. It's likely that metals from re-entering spacecraft mix with and condense onto meteoric smoke particles (MSP) descending from higher altitudes. Further coagulation likely occurs as these particles continue their descent into the stratosphere. Besides, aluminium and other novel elements found in stratospheric aerosols might influence the formation (nucleation) of ice or nitric acid trihydrate (NAT). This carries significance because even small amounts of these new ice nuclei could drastically alter the development of polar stratospheric clouds (PSC). Prior research supports this idea, showing that substances similar to meteoric inclusions within sulfuric acid can trigger ice formation. Furthermore, studies indicate that metal cations have the ability to induce efflorescence within aerosol particles, critically impacting radiative forcing. In this presentation, I'll discuss the gas-phase chemistry of these anthropogenic metals, offering insights into how they might react and alter the stratospheric aerosol. Finally, by identifying knowledge gaps and outlining the necessary research, we can work towards developing a comprehensive understanding of this emerging environmental issue.