Space pollution, also known as space debris, space waste, space trash, space junk, or cosmic detritus, refers to obsolete human-made items in space, primarily in Earth orbit, that no longer serve a useful purpose.

A new study illustrates how rocket launch air pollution spreads throughout the atmosphere, potentially causing harmful warming at otherwise pristine high altitudes.

 A team of researchers from Cyprus's University of Nicosia researched how carbon dioxide and soot spread in the air when a rocket ascends through the Earth's atmosphere.

The researchers discovered that pollution concentrations in the mesosphere (the layer of the atmosphere between 30 and 50 miles (50 and 80 kilometers)) stay alarmingly high for extended periods of time after each launch. These pollutants include the key greenhouse gas carbon dioxide, which scientists are concerned about because local warming of higher layers of the atmosphere could have far-reaching effects for the Earth's climate.

The researchers based their findings on emissions from one of today's most popular rockets, SpaceX's Falcon 9, which runs on the fossil-based rocket fuel RP1 and liquid oxygen. Exhaust from such rockets contains carbon dioxide and water vapor, as well as various amounts of soot, nitrous oxides, and sulfur. Greenhouse gases such as carbon dioxide, water vapor, and nitrous oxide absorb heat and warm our world.

According to the team's simulations, the passage of a rocket through the mesosphere causes a considerable local and transitory increase in carbon dioxide concentrations.

 "The emitted mass of carbon dioxide as the rocket climbs 1 kilometer [0.6 mile] in altitude in the mesosphere is equivalent to that contained in 26 cubic kilometers [6.2 cubic miles] of atmospheric air at the same altitude," the researchers wrote in a statement, adding that such concentrations are significant.

The circulation of the atmosphere eventually dissipates those greenhouse gases and returns the concentrations to "standard" levels; however, it is unknown how long the concentrations remain elevated and what impact they may have on the temperature of the mesosphere. Other types of impacts of rocket launches on the mesosphere have been described previously. For example, launches of NASA's space shuttles were known to trigger the formation of spectacular polar mesospheres.

According to the Environmental and Energy Study Institute, the impact of rocket launches to greenhouse gas emissions is insignificant, accounting for only 1% of aviation's carbon footprint — which accounts for only 2.4% of yearly world carbon emissions.

 However, the spaceflight industry is expanding, with the number of launches increasing year after year. While the impacts of rocket pollution on the atmosphere are currently understudied, the findings of this study suggest that it may be prudent to keep a close check on the situation.

"We hope that commercial flight companies, such as SpaceX, Virgin Galactic, and the New Shepard, as well as their associated engine manufacturers, will consider these effects in future designs," said the study's co-author Dimitris Drikakis, a multidisciplinary science professor at the University of Nicosia in Cyprus.

They are, in fact. SpaceX and Blue Origin, who constructed the New Shephard rocket, both use methane-based fuel in their next-generation rockets (Starship and New Glenn, respectively). According to the National Academies' Database of Emissions Indices, current research indicates that methane-based fuel is exceptionally effective in burning off during combustion, resulting in very few emissions beyond carbon dioxide, water vapor, and a trace of nitrous oxides.

Rocket exhaust pollution in the upper atmosphere might affect Earth's climate | Space