The "natural enemy" of the ozone layer +1? Beware of the debris from scrapped satellites!

Duan Yuechu Huang Xianghong

Satellites orbiting in low Earth orbit will gradually lose altitude over time and eventually burn up and disintegrate in the intense friction with the atmosphere. In the past few decades, scientists once believed that this was a natural and harmless process. However, the latest research has found that this phenomenon may pose a threat to the ozone layer.

The international journal Scientific American recently published a paper titled "Satellite Mega-Constellations May Threaten Recovery of Ozone Hole", pointing out that the increasing number of satellites in low-Earth orbit may destroy the delicate balance of the protective ozone layer.

When satellites in low Earth orbit are in motion, their altitude will slowly decrease due to friction with the atmosphere, and eventually they will enter the atmosphere, releasing a large amount of gas and particulate matter during the combustion and disintegration process. These substances are very likely to have a negative effect on the ozone layer, thereby increasing ultraviolet radiation on the earth's surface. Excessive ultraviolet radiation may induce a variety of diseases such as skin cancer and cataracts, and at the same time have an adverse impact on the ecosystem. Obviously, protecting the ozone layer is crucial to maintaining the ecological balance of the earth and human health.

Data shows that between 2016 and 2022, aluminum oxide pollution caused by satellite re-entry into the atmosphere increased eightfold. These metal particles continue to accumulate in the stratosphere, which may damage the ozone layer and weaken its ability to absorb ultraviolet radiation. Studies have shown that in sufficient concentrations, aluminum oxide can catalyze the destructive reaction of ozone with chlorine, causing ozone molecules to split. At the same time, aluminum oxide remains intact during this process and can continue to react with ozone, causing continuous damage to the ozone layer.

Currently, there are about 8,100 satellites in operation in low Earth orbit, and the Starlink satellites launched by SpaceX, a US space exploration technology company, account for the majority, with a number of up to 6,000. SpaceX also plans to launch up to 42,000 satellites in the future to build its huge Internet satellite network. In addition, other companies around the world, such as Amazon, are also actively preparing to launch tens of thousands of low-Earth orbit satellites. The lifespan of these Internet satellites is generally short, about 5 years. Scientists estimate that when all the planned satellites are launched and reach the end of their service life, nearly 360 tons of aluminum oxide particles will fall into the Earth's atmosphere each year, which is more than 6 times the number of aluminum oxide particles normally present in the atmosphere.

In the face of this emerging threat, there is an urgent need to update the existing regulatory framework to fully consider the potential impacts of satellite re-entry.

On September 16, 1987, the United Nations Environment Programme held an international conference on the protection of the ozone layer in Montreal, Canada, and adopted the Montreal Protocol (hereinafter referred to as the Protocol). The Protocol stipulates the types of controlled substances and the elimination schedule, requiring countries to gradually reduce and eventually stop the production and use of substances such as chlorofluorocarbons that are destructive to the ozone layer. Since the implementation of the Protocol, the production and use of substances that deplete the ozone layer have been successfully reduced worldwide, the trend of ozone layer depletion has been effectively curbed, and an important contribution has been made to protecting the earth's ecological environment.

The success of the Protocol shows that through global collaboration, we can address complex environmental issues. However, the current rules for orbital activities do not seem to provide a simple and effective solution to this difficult problem.

In order to reduce the potential threat to the ozone layer from satellite decay, we should minimize the use of harmful substances during satellite design and manufacturing. When the satellite reaches the end of its life, we can minimize the damage to the ozone layer by precisely controlling its combustion process. In addition, the international community should strengthen cooperation and work together to research and develop more environmentally friendly satellite disposal technologies.

(The author Duan Yuechu is a member of the China Science Writers Association, and Huang Xianghong is a member of the Hunan Science Writers Association)