Two experts warn: Satellite mega-constellations can be dangerous for the earth’s atmosphere. Especially “Starlink” from SpaceX is a thorn in their side.
Satellite mega-constellations such as “Starlink” from SpaceX promise people good things – for example, fast internet in all corners of the world. But the more satellites orbit the earth, the more science deals with the topic and points not only to the effects of the brightly shining satellites on the night sky and astronomy, but also to completely different side effects.
In a study that was published in the journal “Scientific Reports”, the authors warn: Discarded satellites of the “Starlink” mega-constellation could bring more aluminum into the upper atmosphere than meteoroids. “They could become the dominant high altitude source of alumina,” write Aaron Boley and Michael Byers of the University of British Columbia in Vancouver, Canada. Every day, 60 tons of material fell from meteoroids into the earth’s atmosphere, Boley told Space.com. “With the first generation of Starlink, we expect around 2.2 tons of dead satellites to enter the earth’s atmosphere every day,” continues Boley. The difference, however, is serious: Meteoroids consist mainly of stone, which is composed of oxygen, magnesium and silicon. “The satellites, on the other hand, are mainly made of aluminum.”
Discarded “Starlink” satellites from SpaceX bring aluminum into the upper atmosphere
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If the aluminum burns when a satellite enters the earth’s atmosphere, aluminum oxide (alumina) is formed. And this is where it starts to get problematic: “Alumina reflects light of certain wavelengths and if you have enough alumina in the atmosphere, scattering occurs and the earth’s albedo may change,” warns Boley further. Albedo is the reflectivity of a surface that does not illuminate itself.
Dying satellites: “Geoengineering without supervision or regulation”
In fact, in the past there was the idea of using chemicals in the upper atmosphere to change the albedo of the earth in such a way that global warming is slowed down – such ideas fall under the catchphrase “geoengineering”. However, there are strong reservations about not knowing enough about side effects. “Now it looks like we’re doing this experiment without supervision or regulation,” Boley criticized Space.com. “We don’t know what the thresholds are and how that will change the upper atmosphere.”
The aluminum from the burning satellites could also damage the ozone layer. Boley and Byers quote other researchers who have already determined local damage to the ozone layer, which is said to have been caused by missiles flying past. “We know that aluminum oxide itself breaks down ozone through rocket launches, since many solid rocket rockets have aluminum oxide as a by-product,” emphasizes Boley. This would create “small temporary holes in the stratospheric ozone layer”. “This is one of the biggest concerns about changes in the atmosphere that space travel can cause,” continues Boley. SpaceX is currently sending a “Falcon 9” rocket with 60 “Starlink” satellites into orbit about every two weeks.
First “Starlink” generation: the number of satellites in orbit has increased by 50 percent
In their study, Boley and Byers only looked at the effects of the first “Starlink” generation. This means those almost 12,000 satellites for which SpaceX already has a permit. More than 1,700 of these “Starlink” satellites are already orbiting the earth, and Elon Musk’s private space company has long since become the largest satellite operator. The rapid increase in the number of “Starlink” satellites, the first of which were launched in 2019, also worries the scientists for other reasons: According to the scientists, the number of active and inactive satellites in low Earth orbit (orbits less than 1000 kilometers) is within increased by more than 50 percent in two years.
Satellite mega-constellation: SpaceX is planning 55,000 “star links” in Earth orbit
And there is no end in sight: SpaceX has plans to have a total of around 55,000 “Starlink” satellites orbit the earth and other companies want to follow suit: Oneweb is working on its own constellation, Amazon is working on “Project Kuiper” – another one Satellite constellation that is supposed to offer fast Internet – China is planning its own satellite constellation and the EU is also showing interest and is currently having a study carried out on the subject. “That could lead to unprecedented changes in the upper atmosphere,” criticized Boley to Space.com
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Many satellites in earth orbit: the risk of collisions increases
The large number of satellites in earth orbit is not only a problem for Boley and Byers, even before the study was published, criticism was often leveled at the many new satellites that increase the risk of collisions in orbit and, in the worst case, trigger “Kessler syndrome” , in which it comes to a cascade of collisions in space, whereby more and more small pieces of space junk arise, which in turn could threaten active satellites. Just recently, for example, the ISS was hit by a piece of space junk, and the space station had to avoid pieces of junk several times in 2021.
SpaceX’s “Starlink” satellites have been causing a stir since their first launch in 2019. Shortly after their launch, the satellites can be seen again and again as brightly shining “fairy lights” in the sky, causing problems for professional and amateur astronomers from the start. SpaceX is now working with affected experts to limit the impact on the night sky – but so far there have only been partial successes. (Tanja Banner)