The re-entry of the satellite constellations into atmosphere, when they lose their useful life, it can increase the damage to the ozone layer – a problem that scientists at the University of British Columbia, in Canada, have been referring to as “Ozone 2.0”.
According to a survey signed by Aaron Boley, associate professor of astronomy e astrophysics Within the institution, our knowledge of the effects of re-entry of satellites and other human artifacts into the ozone layer differs from those caused, for example, by natural celestial bodies, in ways we do not yet know.
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"We have about 60 tons of meteoroid material hitting us every day," Boley told Science.com. “With the first generation of Starlink [the constellation that offers satellite internet from SpaceX], we can expect more than two tons of dead satellites to enter the atmosphere every day. But while meteoroids are mostly stones – made of oxygen, magnesium and silicon, these satellites are practically made of aluminum, an element that meteoroids have in just 1% [of their composition].”
The problem with this is that burning aluminum generates aluminum oxide – also known as “alumina” – which can trigger effects still unknown to us: “Alumina reflects light at certain wavelengths and if you dump too much of it in the atmosphere, you'll end up creating a spray effect that will eventually change the planet's albedo,” Boley said.
"Albedo" is the reflection coefficient of light, calculated by a very specific formula, which serves to measure the volume of light that is reflected by a given material. In the past, it has been suggested that raising the Earth's albedo would be a solution to slowing global warming. Experts, however, dismissed the thesis, noting that there is almost no knowledge about the side effects of such action.
“Now” – says Boley – “it looks like we are going to conduct this experiment without any regulation or supervision. We don't know what the limit is, or how it's going to change the atmosphere.”
One of the effects we are aware of, however, is the harmfulness of alumina to the ozone layer that permeates the Earth's atmosphere. A problem known for decades is the fact that holes in this layer let ultraviolet rays from the Sun without any kind of filter - which can cause serious problems for humans, like skin cancer.
In their study, Boley and his team cite another research, conducted by the Aerospace Corporation, that identified localized damage to the ozone layer, resulting from the passage of rockets by the atmosphere.
“We know that alumina promotes ozone depletion only by launching rockets – much of the fuel they use has alumina or produces it as a by-product,” Boley said. "This creates 'temporary holes' in the ozone layer."
According to experts, meteoroid and satellite materials, during reentry, burn at an altitude of between 90 and 50 kilometers (km). By itself, this would be enough to reach the ozone layer (mostly located in the stratosphere, between 10 and 60 km from Earth). But even when this does not happen, there is still a risk that particles and other debris that detach from the burning caused by the re-entry could fall into the region.
According to Boley, this effect can cause adverse chemical reactions, triggering ozone depletion.
With companies like SpaceX, Blue Origin and so many others launching rockets, satellites and other objects into space, the specialists' concerns seem to find a plausible foundation, adding yet another theme to the long debate of “space pollution”.
For now, however, this race by companies is not expected to end: only in 2021, SpaceX already have at least four more releases confirmed, while Jeff Bezos, the CEO of Blue Origin, intends to travel - himself - to space in July.
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