The environmental impacts of spaceflight are becoming increasingly apparent as more and more spacecraft are launched into Earth’s orbit.
The growing number of satellites burning up in Earth’s atmosphere has worried scientists for years, and now a new paper explores how the emerging shell of “conductive dust” around the planet, resulting from satellite re-entry, could the Earth’s protective magnetic field.
“We are surrounding the planet with trash,” Sierra Solter-Hunt, an American physicist and PhD student at the University of Iceland, told Space.com. Solter-Hunt is the sole author of the new paper, which was published as a pre-print on the online repository Arxiv in December 2023 and is still awaiting peer review. Since then, the paper has sparked online discussions. Solter-Hunt is happy with that, even if some find her conclusions exaggerated.
“I wanted to get the conversation going,” she said.
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Solter-Hunt came across the problem of increasing concentrations of metal dust in the Earth’s upper atmosphere during her PhD research into ‘plasma dust’. Plasma dust, she explains, is created by interactions between the fragile ionized gas that makes up Earth’s upper atmosphere and the microscopic ash particles left behind from the combustion of meteors that strike the planet, as well as from satellites that spin back after running out of energy. have more. fuel at the end of their missions.
Meteors have been hitting Earth since the beginning of time, but their chemical composition is completely different from that of satellites.
“Meteors contain only trace amounts of highly conductive metals,” Solter-Hunt said. “Satellites, on the other hand, are basically made entirely of superconducting metals.”
According to Solter-Hunt’s calculations, 50 tons of space rock evaporates into Earth’s atmosphere every day, leaving behind about 450 kilograms of charged dust. That’s three times less than what a single returning Starlink satellite generates. Currently, about one old satellite decays in Earth’s atmosphere every day. This was reported by the National Oceanic and Atmospheric Administration. But as mega-constellation operators like SpaceX’s Starlink continue to expand their fleets, that number will only increase.
If SpaceX completes its second-generation Starlink constellation of 42,000 satellites as planned, Starlink satellites alone will re-enter at a rate of 23 per day. That’s because SpaceX plans to regularly upgrade its fleet with newer, more capable spacecraft.
“This is approximately 29 tons of material returning to satellites every day, just for the Starlink mega-constellation alone,” Solter-Hunt said.
The researcher said that with current technology it is difficult to model how exactly this amount of conductive material will affect the Earth’s magnetic field.
“Satellites are usually made of aluminum and aluminum is a superconductor,” Solter-Hunt said. “Superconductors are used to block, distort or shield magnetic fields. My concern is that this conductive dust could cause some disturbances in the magnetosphere at some point in the future.”
At this point, the returning man-made debris has already created more conductive dust than the mass of Earth’s Van Allen radiation belts, two regions above the planet where charged particles from the Sun accumulate thanks to the effects of the magnetic field of the planet.
The inner and outer Van Allen belts extend between altitudes of 3,700 miles and 7,400 miles (6,000 and 12,000 kilometers) and 16,000 and 28,000 miles (25,000 to 45,000 km), respectively. In contrast, the magnetic dust from re-entering satellites accumulates much lower: about 37 to 50 miles (60 and 80 km) above the Earth’s surface.
Solter-Hunt thinks the disruptions caused by the conductive shell could poke holes in Earth’s protective magnetic shield, potentially allowing more harmful cosmic rays to reach the planet’s surface. In an extreme, near-apocalyptic scenario, the weakened magnetosphere could cause the solar wind to begin stripping away Earth’s atmosphere, as happened to Mars’ atmosphere billions of years ago. However, that is certainly not an immediate threat.
Solter-Hunt is more concerned about the effects on the ozone layer. When the aluminum from the satellites burns, it turns into aluminum oxides, a known ozone-depleting substance.
The danger that debris from mega-constellations poses to the ozone layer has been previously investigated by a research team led by Aaron Boley, associate professor of astronomy and astrophysics at the University of British Columbia, Canada.
Boley, whose paper was published in the prestigious journal Scientific Reports, declined to comment in detail on Solter-Hunt’s paper but said it “opens an important discussion.”
However, Karen Rosenlof, an atmospheric chemistry scientist at NOAA who has published papers on the effects of aluminum oxides from satellites re-entering Earth’s upper atmosphere, says the conclusions should be approached with caution.
Scientists, including Rosenlof and Boley, have previously raised concerns about increasing concentrations of satellite ash in Earth’s atmosphere and its long-term impact on the planet.
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There will be another team in October 2023 reported detecting particles originating from rocket exhaust or burned space debris at an altitude of 19 km above the Earth’s surface using NASA’s high-altitude research aircraft.
Researchers think that because of their tiny size, these particles stay in the atmosphere forever or take a very long time to fall back to Earth. With the increasing number of rocket launches and satellite flights, their concentrations are likely to increase sharply.
Like the increasing concentrations of greenhouse gases in the Earth’s atmosphere, the consequences may not become apparent for decades.
“These mega-constellations will continually cause pollution,” Solter-Hunt said. “There’s going to be more and more of it and it’s going to cause a number of different chemical reactions and we don’t really have an understanding of it.”