NOAA cites the environmental impact of rockets in Earth's stratosphere

Photo by Matteo Fusco on Unsplash

Dry, stable air in Earth's stratosphere is like a parking lot for aerosols, fine atmospheric particles that can affect the climate below. During high-altitude flights  over the Arctic by the National Oceanic and Atmospheric Administration this year, researchers collected and analyzed these particles.

Their analysis, published this month in the journal PNAS, relied on a portable mass spectrometer to measure the chemical composition of particles in flight, allowing  scientists to determine chemical signatures elements embedded in individual particles of sulfuric acid, which make up the majority of particles in the stratosphere.

“Two of the most surprising elements we observed in these particles were niobium and hafnium. “ said Daniel Murphy, lead researcher in NOAA. These are two rare elements that we did not expect to be in the stratosphere. The mystery is where these metals come from and how they got there.

Although unusual, such elements are common in spacecraft construction and can be found in semiconductors, rocket chambers, and other applications. The discovery highlights the environmental consequences of a growing number of rockets, satellites and other man-made spacecraft releasing metal vapors as they reenter the atmosphere.

Researchers have also identified aluminum, lithium, copper and lead in the stratosphere, all of which are associated with alloys used in the aerospace industry.

They estimate that about 10% of the sulfuric acid particles studied contained traces of metals from spacecraft re-entry, but researchers warn that this number could reach 50% or more due to the expected increase from satellite launches. They write that someday, the number of aerosols associated with space debris will be greater than the number of particles produced when meteorites evaporate upon entering Earth's atmosphere.

It is unclear exactly how the presence of these rare metals and other elements in the stratosphere may affect climate. Although the researchers wrote that “direct health or environmental impacts at ground level are unlikely,” they said the metals could influence cloud formation, causing light scattering and changes in the composition of the stratosphere over time.