Why satellite space junk may be bad news for the environment

Polluting satellites

Daniel Murphy, an atmospheric scientist at the US National Oceanographic and Atmospheric Administration (NOAA), and others presented definitive evidence that “10% of the aerosol particles in the stratosphere contain aluminum and other metals that originated from the burn-up of satellites, and rocket stages during reentry”(‘Metals from spacecraft reentry in stratospheric aerosol particles’, 2023).

Connor Barker, an atmospheric chemist from the University College of London, and others found that emissions of aluminum and nitrogen oxides from satellite reentries significantly increased from 3.3 billion grams in 2020 to 5.6 billion grams in 2022. Also on the rise were emissions from rocket launches, which leave pollutants such as black carbon, nitrogen oxides, carbon monoxide, aluminum oxide and a variety of chlorine gases (‘Developing inventories of by-products from satellite megaconstellation launches and disposal to determine the influence on stratospheric ozone and climate’, 2024).

Impact of satellite pollution

While pollution from burnt-up satellites high up in the atmosphere is seemingly a distant concern for humans, it might lead to ripple effects that will change the chemistry of the atmosphere. This is not good news. Life on Earth has evolved over billions of years to adjust to the planet’s specific environment, and even miniscule changes could trigger massive chaos on the planet.

Scientists are particularly concerned about the impact of this pollution on the ozone layer in Earth’s stratosphere. This layer absorbs up to 99% of ultraviolet rays from the Sun, which would otherwise harm living organisms on Earth’s surface.

But pollutants from burnt-up spacecraft are likely already harming it. Aluminum oxide, for instance, is a known catalyst for ozone depletion. This would be major new threat to the ozone layer especially in the light of the success of the Montreal Protocol of 1987, which banned production and emissions of known ozone-destroying chemicals such as chlorofluorocarbons (CFCs), previously used as a common refrigerant.

Murphy also notes many other ways in which spacecraft pollutants might impact the atmospheric composition. He told Science News: “Soot emitted from rocket engines absorbs solar energy, which can warm the atmosphere. Copper and other metals released during the incineration of spacecraft wiring and alloys are known to be powerful catalysts for chemical reactions in the atmosphere. Among other things, those metals could promote the creation of the tiny particles that act as the seeds of clouds.”