The projected growth in rocket launches for space tourism, the return to the Moon, and subsequent trips to Mars could damage the protective ozone layer on Earth.
A US NOAA (National Oceanic and Atmospheric Administration) study argues that kerosene-burning rocket engines widely used by the global launch industry emit exhaust gases containing black carbon, or soot, directly into the stratosphere, where is the ozone layer located This layer protects all living things on Earth from the harmful effects of ultraviolet radiation, including skin cancer and immunosuppression in humans, as well as from disturbances in agriculture and ecosystems.
According to the study published in the Journal of Geophysical Research: Atmospheres, a 10-fold increase in hydrocarbon-fueled launches, which is plausible over the next two decades based on recent trends in space traffic growth, would damage the of ozone and would change patterns of atmospheric circulation.
“We need to learn more about the potential impact of hydrocarbon-burning engines in the stratosphere and on Earth’s surface climate,” lead author Christopher Maloney, a CIRES research scientist working in the Science Laboratory, said in a statement. . NOAA Chemists. “With more research, we should be able to better understand the relative impacts of different types of rockets on climate and ozone.”
Launch rates tripled
Launch rates have more than tripled in the past few decades, Maloney said, and accelerated growth is projected for decades to come. Rockets are the only direct source of man-made aerosol pollution above the troposphere, the lowest region of the atmosphere, which extends four to six miles above the Earth’s surface.
The research team used a climate model to simulate the impact of approximately 10,000 metric tons of soot pollution injected into the stratosphere over the Northern Hemisphere each year for 50 years. Currently, about 1,000 tons of rocket soot are emitted annually. The researchers caution that the exact amounts of soot emitted by the different hydrocarbon-fueled engines used around the world are not well known.
how rocket exhaust affects the ozone layer
The researchers found that this level of activity would increase annual temperatures in the stratosphere by between 0.5 and 2 degrees Celsius, which would change global circulation patterns by slowing subtropical jet streams by up to 3.5 per cent and weaken the stratospheric overturning circulation.
Stratospheric ozone is strongly influenced by temperature and atmospheric circulation, noted co-author Robert Portmann, a research physicist at the Chemical Sciences Laboratory, so it was not surprising to the research team that the model found changes in stratospheric temperatures and winds. it will also cause changes in ozone abundance.
The scientists found that ozone reductions occurred poleward of 30 degrees north, or around the latitude of Houston, almost every month of the year. The maximum reduction of 4% occurred at the North Pole in June. All other locations north of 30°N experienced at least some ozone depletion throughout the year. This spatial pattern of ozone loss directly matches the modelled distribution of black carbon and the warming associated with it, Maloney explained.
“The bottom line is that projected increases in rocket launches could expose people in the Northern Hemisphere to more harmful ultraviolet radiation,” Maloney said.
The research team also simulated two larger emission scenarios of 30,000 and 100,000 tons of soot pollution per year to better understand the impacts of an extremely large increase in future space travel using hydrocarbon-fueled engines and to more clearly investigate the reactions that determine the response of the atmosphere. The results showed that the stratosphere is sensitive to relatively modest injections of black carbon. Larger emissions simulations showed similar but more severe disruptions in atmospheric circulation and weather losses than the 10,000-metric-ton case.
The study was based on previous research conducted by members of the author team. A 2010 study led by co-author Martin Ross, a scientist at The Aerospace Corporation, explored for the first time the climate impact of an increase in soot-producing rocket launches. A second study conducted at NOAA in 2017, of which Ross is a co-author, examined the climate response to water vapour emissions from a proposed reusable space launch system using cleaner hydrogen-powered rockets.
“Our work emphasizes the importance of ozone depletion caused by soot particles emitted from liquid-fueled rockets,” Ross said. “These simulations change the old belief that the only threat to the ozone layer from spaceflight was solid-fuel rockets. We’ve shown that the particles are where the action is for spaceflight impacts.”
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