IIt is easy to understand how the flame and power of rocket launches can cause air pollution. Less obvious is the air pollution caused by rocket parts, spacecraft and satellites re-entering the atmosphere.
A new one global inventory cataloged air pollution from space activities from 2020 to 2022. The inventory includes time, position and contamination of 446 launchers as they took off and the traces of re-entry as objects are heated to extreme temperatures and break up or burn up in the upper atmosphere.
It catalogs the contamination from 63,000 tons of rocket propellants used in 2022 and from 3,622 objects, including rocket parts and satellites, that re-entered the atmosphere between 2020 and 2023, amounting to about 12,000 tons.
Dr Connor Barker, from the UCL team, said: “Many rocket manufacturers and space agencies keep this information tightly controlled. We had to be creative about the different sources we consulted, from launching live streams on YouTube to online databases maintained by space enthusiasts in their spare time.”
Between the late 1960s and 2016, 100 to 200 objects were launched into space per year, but the arrival of mega-constellations of communications satellites set new records. Systems including Starlink, OneWeb, star shield and A Thousand Sails consists of satellites that require low orbits to reduce signal delays. These link together to give global coverage.
Barker said: “We were most surprised by the increase in material falling back to Earth – discarded rocket parts and discarded satellites at the end of their lives – and how fast the emission from mega-constellations is growing, given that the first launches were only in 2019 . “
Types of launch pollutants depend on the propellant, but can include particles of soot and aluminum oxides as well as nitrogen oxides, chlorine and water vapor and carbon dioxide. Extreme heat on reentry causes atmospheric oxygen and nitrogen to combine to form more nitrogen oxides and also produces small metal oxide particles as the objects break and burn.
Soot emitted high into the atmosphere can persist for several years, with a resulting climate warming impact of up to 500 times larger than the same amount of soot from aviation or ground level sources. Aluminum oxide particles, nitrogen oxides and chloride can consume the ozone in the stratosphere that protects us from the sun’s ultraviolet radiation. It can remain in the atmosphere for decades.
