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Now there's one more reason to criticize Musk.

As the number of low-orbit satellites, such as Starlink, surges, they could damage the ozone layer to a degree that could undo the gains made over the past few decades through the Montreal Protocol, a new study predicts.

Blame it on Musk

Aluminum is one of the most common materials in satellites and launch vehicles. When a low-orbit satellite completes its mission, it will leave orbit and enter the atmosphere to burn and disintegrate. During this process, a large number of aluminum oxide nanoparticles will be released due to intense friction and high temperature. These particles are mainly formed in the mesosphere at 50 to 85 kilometers, and gradually move downward to the stratosphere where the ozone layer is located.

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In fact, aluminum oxide itself does not react directly with ozone molecules, but catalyzes the reaction between ozone and chlorine, and the active chlorine produced therefrom destroys the ozone molecules.

Researchers found [1] thatTaking a typical small satellite (250 kg) as an example, it will release about 30 kg of aluminum oxide particles when it re-enters the atmosphere.The researchers further estimated that about 17 tons of aluminum oxide particles were released into the mesosphere based on the number of low-orbit satellites that fell into the atmosphere in 2022. Considering that the competition for orbital resources will be more intense in the future,More than 360 tonnes of alumina will be released into the atmosphere each year.

Researchers calculated through models that it would take about 30 years for aluminum oxide particles released by satellites to reach the stratosphere where ozone is located from the mesosphere. This means that the ozone destruction effect catalyzed by aluminum oxide has a certain lag [1].

These data suggest that as the number of satellites in low-Earth orbit continues to increase, the depletion of the ozone layer from aluminum oxide released by their burning could offset the gains made over the past few decades through the Montreal Protocol.As of 2022, satellites falling into the atmosphere have increased the amount of aluminum in the atmosphere by 29.5%.

However, the researchers also pointed out thatBecause it is almost impossible to obtain data on aluminum oxide produced by satellite burning in reality, the model assumes the maximum production of aluminum oxide particles, which is the "worst case scenario."

All efforts in vain?

In the 1970s, scientists first discovered that man-made compounds such as chlorofluorocarbons (CFCs) decompose in the atmosphere, releasing chlorine atoms that can react with ozone and cause ozone layer depletion. These discoveries have attracted widespread attention and research.

The theory was first proposed in 1974 by scientists Mario Molina and Sherwood Rowland.

In 1985, Joe Farman and others from the British Antarctic Expedition discovered through ground observation equipment that the ozone concentration over Antarctica had significantly decreased.

Subsequently, NASA satellite data confirmed this observation, further confirming the existence of a severe ozone hole over Antarctica.

The formation of the ozone layer is a complex natural process. Ultraviolet radiation from the sun interacts with oxygen molecules (O₂) in the stratosphere, breaking them into two oxygen atoms (O). These oxygen atoms then combine with other oxygen molecules to form ozone (O₃).

This process continues, forming a dynamic balance, thus maintaining the stability of the ozone layer. Ozone can absorb the sun's ultraviolet rays (UVB-C and UVB-B) to protect plants and animals. At the same time, ultraviolet rays absorbed by the ozone layer will be converted into heat, causing the temperature of the stratosphere to rise, thereby affecting the earth's climate system and playing a role in regulating the climate.

Therefore, the discovery of the ozone hole prompted the international community to take action.This ultimately led to the signing of the 1987 Montreal Protocol, an agreement aimed at phasing out ozone-depleting substances, including CFCs.

Arctic ozone hole during the warmer-than-normal years of 1984 and the extremely cold 1997 | Canadian Space Agency

Ozone recovery is a long process. You may wonder, since the Montreal Protocol banned the production and use of ozone-depleting substances nearly 40 years ago, the content in the atmosphere should be very low, right?

Ozone-depleting substances are extremely inert and can exist for decades or even hundreds of years if they are released into the atmosphere in large quantities. The concentration of these substances in the atmosphere has only slowly decreased since around 2000.

However, attention has played a positive role. According to the Scientific Assessment Report on Ozone Depletion released in 2022 [2], stratospheric ozone is still recovering.

Ozone Depletion Substances Time Trend Chart丨Ozone Depletion Scientific Assessment Report

Total column ozone (the sum of all ozone molecules in the vertical column of space in the atmosphere from the surface to the top of the atmosphere) is projected to return to 1980 levels around 2066 in the Antarctic and around 2045 in the Arctic, while the global average (60°N–60°S) is projected to return around 2040.

However, this report does not take into account the potential impact of low-orbit satellites.

How many crimes?

More and more scrapped satellites, as well as the fragments produced by their disintegration and explosion, and the "remains" after satellite collisions, have become what people call "space junk". Space junk affects people's space exploration. Working spacecraft must also be vigilant to avoid them at all times to prevent more serious chain collisions.

Space junk separation belt | NASA

There is another explanation for the "mega-constellation". A large number of satellites in orbit have become artificial "stars" in the night sky - people can see fewer and fewer pure nights. Scientists such as Samantha M. Lawler (2021) observed and simulated 65,000 satellites and found that 50° north and south latitudes are the "hardest hit areas" of "light pollution". At certain times of the night, satellites account for up to 8% of the visible light source.

Light pollution caused by low-Earth orbit satellites and space debris interferes with ground-based astronomical observations, affecting the accuracy of data and the progress of scientific research[3]. Even the selection of sites for observatories has become a problem.

Starlink satellites leave streaks on astronomical photos | National Optical-Infrared Astronomy Research Laboratory

Fortunately, major companies are working with scientists to develop new technologies to reduce the reflectivity of satellites and thus reduce the light pollution. Some companies are even going into space to capture and process space junk.

Regarding the damage to the ozone layer, we need more real data as evidence to prove the extent and how these satellites in the sky will affect it, so as to find countermeasures. Currently, no company competing in the "space race" for satellite internet (not just SpaceX) has responded to this "potential impact".

Low-orbit constellations have played an important role in Internet coverage, meteorological observation, disaster monitoring, navigation and scientific research. However, it is often difficult for technology promoters to control the direction of technology.

Starlink brings satellite broadband services to remote areas and developing countries, but it only took two days for a primitive Amazon tribe called Marubo to go from believing in shamanism and witchcraft to becoming addicted to pornographic websites.

References

[1] Ferreira, J. P., Huang, Z., Nomura, K.-i., & Wang, J. (2024). Potential ozone depletion from satellite demise during atmospheric reentry in the era of mega-constellations. GeophysicalResearch Letters, 51, e2024GL109280. https://doi.org/10.1029/2024GL109280

[2] Scientific Assessment of Ozone Depletion: 2022 - Executive Summary:https://library.wmo.int/records/item/42105-scientific-assessment-of-ozone-depletion-2022-executive-summary

[3] Lawler, Samantha M., Aaron C. Boley, and Hanno Rein. "Visibility predictions for near-futuresatellite megaconstellations: latitudes near 50 will experience the worst light pollution." The Astronomical Journal 163.1 (2021): 21.