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There are now warnings that if projects for launching tens of thousands of satellites such as SpaceX Starlink proceed as planned, eventually chemicals released as dead satellites plunge back to Earth could cause serious damage to the ozone layer. Scientists also say that poorly understood atmospheric processes can be triggered by satellite reentry. This could lead to unintended geoengineering experiments with unknown consequences.
Up to the present, the space industry was satisfied that the amount of material that burns in the atmosphere as a result of fall of huge quantities of micrometeorites is far greater that the mass of materials contributed by falling satellites. However, the chemical composition of micrometeorites is very different than the composition of satellites.
Aaron Boley is an associate professor of astronomy and astrophysics at the University of British Columbia, Canada. He is the author of a paper just published in the journal of Scientific Reports. In an interview, he said, “We have 60 tons of meteoroid material coming in every day.” Boley, one of the authors of a paper published May 20 in the journal Scientific Reports, said, “With the first generation of Starlink, we can expect about 2.2 tons of dead satellites reentering Earth's atmosphere daily. But meteoroids are mostly rock, which is made of oxygen, magnesium and silicon. These satellites are mostly aluminum, which the meteoroids contain only in a very small amount, about 1%.”
The research team realized that the huge concentration of communication satellites in orbit have the potential to modify the chemistry of the upper atmosphere. The burning of aluminum produces aluminum oxide also called alumina which can trigger more unexplored side effects. Boley said, “Alumina reflects light at certain wavelengths and if you dump enough alumina into the atmosphere, you are going to create scattering and eventually change the albedo of the planet.”
The term albedo refers to the amount of light that a particular material reflects. Injecting specific types of chemicals into the higher levels of the atmosphere has been suggested as a possible geoengineering solution that could reduce global warming. However, Boley said that the scientific community has rejected such experiments because the possible unforeseen consequences. He said, “Now it looks like we are going to run this experiment without any oversight or regulation. We don't know what the thresholds are, and how that will change the upper atmosphere."
The burning aluminum from falling satellites is understood to have the potential to damage the ozone layer. This is a well-known problem which has been successfully treated by bans on the use of chlorofluorocarbons. These chemicals have been utilized in the past in aerosol sprays and refrigerators.
In the paper published by Boley’s team, they cite research by their counterparts at the Aerospace Corporation (AC), a U.S. non-profit research organization. The AC research identified local damage to the Earth’s ozone layer that was triggered by the passage of polluting launch vehicles as they rose through the atmosphere.
Boley said, “We know that alumina does deplete ozone just from rocket launches themselves because a lot of solid-fuel rockets use, or have, alumina as a byproduct. That creates these little temporary holes in the stratospheric ozone layer. That's one of the biggest concerns about compositional changes to the atmosphere that spaceflight can cause.”
The ozone layer protects life on Earth from dangerous ultraviolet radiation. It is the second lowest layer in the atmosphere. It extends from seven miles above the surface to forty miles. Depletion of the ozone layer leads to an increased risk of cancer and eye damage to people on Earth.
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