The concentration of ozone-destroying aluminum oxide in Earth's atmosphere could rise by as much as 650% in the coming decades due to a surge in the number of defunct satellites that will burn up during re-entry, a first-of-its-kind study has found. And, as satellite megaconstellations continue to pique the interest of private companies, this could be very bad news for our planet's protective shield known as the ozone layer.
The study authors say that increasing concentrations of satellite-borne pollutants could cause “potentially significant” ozone depletion, and thus hinder the slow and steady recovery of the ozone layer.
First, the ozone layer needs to heal because a hole was created in the layer over Antarctica in the 1980s, caused by the use of chlorine and fluorine-containing gases in refrigerants and aerosol sprays. However, the hole is healing thanks to the Montreal Protocol, which banned these offending substances in 1987. But, if the team's new study is correct, this healing process could soon face a major obstacle due to a new man-made threat: megaconstellations. In short, megaconstellations are groups of hundreds (sometimes thousands) of individual satellites that work together.
In recent years, Scientists have begun to express concern About the growing number of satellites burning up in Earth's atmosphere. Spacecraft bodies are made of aluminum, which gives rise to ozone-destroying aluminum oxide when burned. The new study, conducted by researchers at the University of Southern California (USC), Los Angeles, is the first to model the origin of these pollutants in the atmosphere and estimate the evolution of their concentrations based on the predicted spread of satellites.
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“This study used molecular dynamics simulations at the atomic scale to determine the amount of aluminum oxide generated for a model satellite reentry, and then estimated the amount of aluminum oxide that would be generated in the future using the number of reentry satellites planned for a satellite megaconstellation,” Joseph Wang, professor of astronautics and of aerospace and mechanical engineering at USC and corresponding author of the study, told Space.com.
The researchers found that in 2022, about 332 metric tons of old satellites burned up in the atmosphere, producing 17 metric tons of aluminum oxide particles in the process. Between 2016 and 2022, the concentration of these oxides in the atmosphere increased eightfold and will continue to rise even more with the growing number of satellites launched and reentering.
According to the European Space AgencyThere are currently about 12,540 satellites orbiting Earth, of which about 9,800 are operational. By the end of this decade, that number could grow tenfold thanks to plans by private companies to build mega-constellations of thousands of internet-beaming, low-Earth orbit satellites. SpaceX’s Starlink mega-constellation, for example, currently includes more than 6,000 spacecraft, and the company plans to deploy a total of 40,000 satellites for the effort. Firms including OneWeb, Amazon and Chinese projects G60 and Guowang are developing their own mega-constellations.
If all of these plans come to fruition, 3,200 metric tons of satellite debris could burn up in the atmosphere each year by 2030. The researchers estimated that as a result, 630 metric tons of aluminum oxide could be released into the upper atmosphere each year, increasing the concentration of these particles by up to 650% compared to natural levels.
Wang said the particles, which first accumulate at an altitude of about 50 miles (85 kilometers), where most of the satellite's material has evaporated, take up to 30 years to reach the height of the ozone layer. Only then will the oxides begin their destructive work. The researchers did not study 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 layer concentrated in the stratosphere At altitudes of nine to 28 miles (15 to 30 km), ozone absorbs harmful ultraviolet (UV) radiation, protecting organisms living on the planet's surface from harm.
Unlike conventional ozone-depleting substances, aluminum oxide particles activate ozone destruction processes without being consumed in the reactions. Therefore, the concentration of these substances remains constant, preventing the oxide from being destroyed, the researchers said. continue They will continue to do their harmful work until they naturally descend to a lower altitude below the ozone layer. However, Wang said this could take up to 30 years.
Although much more meteorite material enters Earth's atmosphere each year than artificial satellites, this natural space rock does not contain aluminum and therefore poses no threat to the ozone layer. The researchers said more research is needed to fully understand the dangers the megaconstellation poses to our planet.
“The chemistry and physics that occur during the cooling and settling of these re-entry byproducts in the atmosphere, including chemical reactions with ozone, are not the subject of this study and are not fully understood by the community,” Jose Pedro Ferreira, a research fellow at USC and lead author of the study, told Space.com in an email. “For this reason, any conclusions concerning environmental effects are premature. These known unknowns should serve as an incentive to devote more resources to this research line, which is currently being pursued by our group at USC.”
the study The report was published June 12 in the journal Geophysical Research Letters.