by The environmental impacts of spaceflight are becoming more apparent as more and more spacecraft are launched into Earth orbit.
Scientists have been concerned for years about the increasing number of satellites burning up in the Earth’s atmosphere, and now a new paper examines how the resulting shell of “conductive dust” around the planet could be affected. satellite re-entries of Earth’s protective magnetic field.
“We are surrounded by trash,” Sierra Solter-Hunt, an American physicist and PhD candidate at the University of Iceland, told Space.com. Solter-Hunt is the sole author of the new paper, published in December 2023 as a preprint on the Arxiv online repository and still awaiting peer review. Since then, the paper has sparked discussion online. Solter-Hunt is happy about that, although some people think her conclusions are exaggerated.
“I wanted to start the conversation,” she said.
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Solter-Hunt encountered the problem of increased concentrations of metallic dust in Earth’s upper atmosphere during her PhD research on “plasma dust.” Plasma dust, she explains, arises from the interactions of the fragile ionized gas that makes up the Earth’s upper atmosphere and the microscopic ash particles left behind by the burning of meteors that hit the planet as well as satellites that recede after takeoff. 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.
“The meters only have trace amounts of highly conductive metals,” said Solter-Hunt. “On the other hand, satellites are essentially entirely made of superconducting metals.”
50 tons of space rocks evaporate in the Earth’s atmosphere every day, leaving behind about 450 kilograms of charged dust, according to Solter-Hunt calculations. That’s three times less than what a single reentry Starlink satellite generates. Currently, about one old satellite dies in the Earth’s atmosphere every day, according to the National Oceanic and Atmospheric Administration. But as mega constellation operators like SpaceX’s Starlink continue to add to their fleets, that number is set to grow.
If SpaceX completes its second-generation Starlink constellation of 42,000 satellites as planned, Starlink satellites alone will be re-entering at a rate of 23 per day. That’s because SpaceX plans to regularly upgrade its fleet with newer, more capable spacecraft.
“This is about 29 tons of satellite reentry material every day, just for the mega-constellation Starlink,” said Solter-Hunt.
The researcher said that with current technology, it is difficult to model exactly how this amount of conductive material will affect the Earth’s magnetic field.
“Satellites are mostly made of aluminum and aluminum is a super conductor,” 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.”
Already at this point, the returning man-made debris has created dust more conductive 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 planet’s magnetic field.
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. On the other hand, the magnetic dust from re-entry satellites accumulates much lower – about 37 to 50 miles (60 and 80 km) above the Earth’s surface.
Solter-Hunt thinks that the perturbations caused by the conductive shell could have poked holes in Earth’s protective magnetic shield, potentially allowing more harmful cosmic radiation to reach the planet’s surface. An extreme, almost apocalyptic scenario could see the weakened magnetosphere allow the solar wind to begin stripping the Earth’s atmosphere as it did the atmosphere of Mars billions of years ago. That is certainly not an immediate threat, however.
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 substance known to deplete ozone.
The danger presented by mega-constellation debris to the ozone layer It has been audited before 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 on Solter-Hunt’s paper in detail, but said it opens up an “important debate”.
Karen Rosenlof, an atmospheric chemist at NOAA who has published papers on the effects of aluminum oxides from satellite re-entries on Earth’s upper atmosphere, said the conclusions should be taken with caution, however.
Scientists, including Rosenlof and Boley, have previously expressed concern about the increasing concentrations of satellite ash in Earth’s atmosphere and how that could affect the planet in the long term.
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In October 2023, another team reported the discovery of particles originating from rocket exhaust or burned space debris at an altitude of 11.8 miles (19 km) above the Earth’s surface using NASA’s high-altitude research aircraft.
Researchers think that these particles stay in the atmosphere forever or take a very long time to fall back to Earth because of their small size. With the increasing rate of rocket launches and satellite flights, their concentration is likely to increase sharply.
Just like the increasing concentrations of greenhouse gases in the Earth’s atmosphere, the consequences may not become apparent until many years from now.
“These mega-remedies are always going to cause pollution,” Solter-Hunt said. “There’s going to be more and more of it and it’s going to be causing a number of different chemical reactions and we basically have no understanding of it.”
