Leonard David's INSIDE OUTER SPACE

Space debris plunges to Earth, burning its way through the atmosphere.
Image credit: The Aerospace Corporation

End-of-life, human-made space scraps that fall into Earth’s atmosphere are leaving behind a train of tiny particles that are eating away at our fragile biosphere.

The new work has been published in the AGU journal Geophysical Research Letters pointing to the increasing number of satellite constellations, the byproducts of which on re-entry catalyze chemical reactions that destroy stratospheric ozone.

The work was led by José Ferreira in the Department of Astronautical Engineering at the University of Southern California (USC), Los Angeles.

Launch and reentry particle emissions in the Earth’s stratosphere.
Image credit: The Aerospace Corporation

Rapid ramp up

“Only in recent years have people started to think this might become a problem,” said Joseph Wang, a researcher in astronautics at USC and a corresponding author of the new work.

“We were one of the first teams to look at what the implication of these facts might be,” Wang said in an AGU media release.

According to Wang and research colleagues, demand for global internet coverage is driving a rapid ramp up of launches of small communication satellite swarms.

Falcon 9 booster topped with sixty Starlink satellites.
Credit: SpaceX

SpaceX and its Starlink satellites is the front runner in this enterprise. Amazon and other companies around the globe are also planning constellations ranging from 3,000 to 13,000 satellites, the authors of the study explain.

Unplanned pollution

Internet satellites in low Earth orbit are short-lived, say about five years. What follows is that companies must then launch replacement satellites to maintain internet service.

What this adds up to is a cycle of planned obsolescence, coupled with unplanned pollution of Earth’s atmosphere.

“Satellites burn up at the end of service life during reentry, generating aluminum oxides as the main byproduct. These are known catalysts for chlorine activation that depletes ozone in the stratosphere,” explains the research paper: “Potential Ozone Depletion From Satellite Demise During Atmospheric Reentry in the Era of Mega-Constellations.”

Molecular dynamics simulations

Wang and research team colleagues note that the environmental impacts from the reentry of satellites are currently poorly understood.

The team’s investigation focuses on the oxidation process of the satellite’s aluminum content during atmospheric reentry utilizing atomic-scale molecular dynamics simulations, cited as the first simulation work to do so.

The simulations were performed at the USC Center for Advanced Research Computing (CARC).

Above natural levels

By applying reentry forecasts considering the deployment of mega-constellations, the aluminum excess ratio at the top of the mesosphere can reach a yearly excess of more than 640 percent above natural levels, they report, or over 360 metric tons of aluminum oxide clusters per year from satellites.

“We find that the population of reentering satellites in 2022 caused a 29.5% increase of aluminum in the atmosphere above the natural level, resulting in around 17 metric tons of aluminum oxides injected into the mesosphere,” the researchers report.

Credit: CORDS/The Aerospace Corporation

Aluminum is one of the most prevailing materials in satellites and launch vehicles by mass.

Future scenario

Moreover, the byproducts generated by the reentry of satellites in a future scenario – where projected mega-constellations come to fruition — can reach over 360 metric tons per year. “As aluminum oxide nanoparticles may remain in the atmosphere for decades, they can cause significant ozone depletion,” the new research adds.

The team calculates that, based on particle size, it would take up to 30 years for the aluminum oxides to drift down to stratospheric altitudes, where 90% of Earth’s ozone is located.

To view this research – “Potential Ozone Depletion From Satellite Demise During Atmospheric Reentry in the Era of Mega-Constellations” – go to:

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GL109280