Concentrations of ozone-depleting aluminum oxides in Earth’s atmosphere could increase by 650% in the coming decades due to an increase in the number of defunct satellites that burn up during re-entry, a first-of-its-kind study has found. And as satellite megaconstellations continue to fuel private corporate interests, this could be pretty bad news for our planet’s protective shield known as the ozone layer.
The authors of the study say that increasing concentrations of satellite-borne pollutants could cause “potentially significant” depletion of the ozone layer, thwarting the slow and steady recovery of the ozone layer.
The ozone layer needs to be restored in the first place because in the 1980s a hole opened up in this layer over Antarctica due to the use of chlorine- and fluorine-rich gases in refrigerants and aerosol sprays. However, the hole is being repaired thanks to the Montreal Protocol, which banned these harmful substances in 1987. However, if the team’s new study is correct, this healing process may soon hit a major roadblock due to a new man-made threat: megaconstellations. In short, megaconstellations are conglomerations of hundreds (sometimes thousands) of individual satellites working together.
In last years, scientists began to express concern about the increasing number of satellites burning in the earth’s atmosphere. The bodies of spaceships are made of aluminum, which produces ozone-destroying aluminum oxides when burned. The new study, conducted by researchers at the University of Southern California (USC), Los Angeles, is the first to model the formation of these pollutants in the atmosphere and estimate the evolution of their concentrations based on the predicted proliferation of satellites.
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“This study used atomic-scale molecular dynamics simulations to quantify the amount of alumina generated for a model satellite reentry, and then used the number of reentrant satellites planned for satellite megaconstellations to predict the amount of alumina that will be generated in the future.” Joseph Wang, professor of aerospace and aeronautical and mechanical engineering at USC and corresponding author of the study, told Space.com.
The researchers found that about 332 metric tons of old satellites burned up in the atmosphere in 2022, creating 17 metric tons of alumina particles in the process. Between 2016 and 2022, concentrations of these oxides in the atmosphere increased eightfold and will continue to rise even higher as more satellites are launched and re-entered.
The European Space Agency claims itThere are currently about 12,540 satellites orbiting the Earth, of which about 9,800 are operational. By the end of this decade, that number could increase tenfold due to plans by private companies to build mega-constellations of tens of thousands of satellites in low Earth orbit. For example, SpaceX’s Starlink mega-constellation currently includes more than 6,000 spacecraft, and the company plans to deploy up to 40,000 satellites in total for the effort. Firms including OneWeb, Amazon and China’s G60 and Guowang projects are developing their own mega-constellations.
If all these plans come to fruition, up to 3,200 metric tons of satellites per year could burn up in the atmosphere by the 2030s. As a result, 630 metric tons of aluminum oxides could be released into the upper atmosphere annually, the researchers estimated, leading to up to a 650% increase in concentrations of these particles compared to natural levels.
Wang said it takes up to 30 years for the particles, which first accumulate at an altitude of about 85 kilometers, where most of the satellite’s material evaporates, to reach the altitudes where the ozone layer resides. Only then would the oxides begin their destructive work. Scientists have not studied the impact on the protective ozone shield in detail. However, they stressed that the effects could be “significant”.
Most of the planet’s protective ozone is concentrated in the stratosphere at altitudes between nine and 28 miles (15 and 30 km). Ozone absorbs harmful ultraviolet (UV) radiation, protecting living organisms on the planet’s surface from damage.
Unlike traditional ozone-depleting substances, the alumina particles trigger ozone-depleting processes without being consumed in the reactions, the researchers said. The concentrations of these substances therefore remain stable, which allows the oxides continue their harmful work until they naturally descend to lower altitudes below the ozone layer. But that could also take up to 30 years, Wang said.
Although far more meteorite material enters the Earth’s atmosphere each year than artificial satellites, this natural space rock contains no aluminum and therefore poses no risk to the ozone layer. Scientists said more research is needed to fully understand the risks megaconstellations pose to our planet.
“The chemistry and physics of these reentry byproducts as they cool and settle in the atmosphere, including chemical reactions with ozone, are not the focus of this study and are not fully understood by the community,” José Pedro Ferreira, a researcher at USC and lead author of the study told Space .com in the email. “For this reason, any conclusions regarding environmental impacts are premature. These known unknowns should act as an incentive to devote more resources to this line of research that our group at USC is currently pursuing.”
Studies was published in the journal Geophysical Research Letters on June 12.