Since the global ban on the use of chlorofluorocarbons (CFCs) in industry, the hole in the Earth's ozone layer, which absorbs most of the sun's ultraviolet rays, has been slowly healing over the past few decades. But now scientists are sounding the alarm about breaking a new hole - this time the chemicals have nothing to do with it.
If earlier the heavy chemical industry was the main threat to the ozone layer of our planet, today the source of the problem is very unusual. According to experts, it's all about the deterioration of the quality of aluminum in the most common satellites, such as SpaceX's Starlink network.
A satellite is an artificial object launched into low-earth orbit for a planned service life. On the pages of Scientific Reports, researchers at the University of British Columbia reported that there are currently about 5,000 active and non-operational satellites in the area, and their number will skyrocket in the near future. Recall that Elon Musk's company plans to launch more than 40,000 Starlink satellites, but do not forget about the many different satellite projects of national space agencies and private companies around the world.
Scientists have been comparing satellite "debris" swirling in the atmosphere for decades to meteorites of various sizes. And although the total volume of meteorite debris was much higher than that of satellite, space rocks did almost no harm to the planet. So why is the ozone layer actively destroyed by man-made satellites?
It turns out that it's all about quality, not quantity.
"Up to 60 tons of meteoroids are in the Earth's atmosphere every day," lead author Aaron Bowley told Space.com. “With the first generation of Starlink, we can expect about 2 tons of dead satellites to circle our planet's atmosphere every day. But meteoroids (that is, space bodies ranging in size from a speck of dust to an asteroid) are mainly composed of rocks, in turn consisting of oxygen, magnesium and silicon. However, satellites are mainly composed of aluminum, which is contained in meteoroids in a very small amount, about 1%."
Aluminum is the key to everything at stake. First, it burns to anhydrous aluminum oxide (aka "alumina"), which can turn into an involuntary geoengineering experiment that can change the Earth's climate. Secondly, aluminum oxide can damage the ozone layer and even break through it.
Alumina scatters more light than glass, with a refractive index of about 1.76 compared to 1.52 for glass and about 1.37 for plain aluminum. Geoengineers have long speculated that the launch of huge satellite networks and, accordingly, the increase in the amount of alumina on the planet as they fail, will change the ability of the Earth to reflect and scatter the light of the Sun. How this will affect the ecology and climate of the planet is anyone's guess.
But what about the ozone layer? Once again, alumina comes to the fore. During combustion, aluminum reacts with ozone in the air, thereby depleting natural reserves of an extremely important gas. The more satellites burn up in the atmosphere, the thinner the ozone layer. Now the consequences for the planet's atmosphere are not so significant, but when it comes to tens of thousands of satellites, it’s time to sound the alarm.
It is worth remembering that satellites are not the only reason for the thinning of the ozone blanket over the planet. Each launch of a rocket that puts satellites into orbit also threatens the protective layer. "Rockets threaten the ozone layer by precipitating radicals right in the stratosphere, with solid-fuel rockets doing the most damage because of the hydrogen chloride and alumina they contain," the researchers write.
The authors of the article admit that bureaucracy and “inadequate” policies governing the end-of-life rules for satellites stand in the way of solving these problems. Moreover, technologies to prevent collisions of satellites with each other and with other "junk" elements in low orbit significantly increase their cost, and therefore are only a recommendation measure - the international committee cannot oblige all satellite manufacturers to put "signals" on their devices.
In conclusion, scientists insist that the Earth's orbit is not only an important, but also simply the ultimate resource of mankind. Light pollution from satellites is already preventing many astronomers from doing their work, but putting thousands and thousands of new vehicles into orbit can have very unpleasant consequences for all of humanity.