As commercial fleets grow, concerns raised about ozone-destroying effects of metal particles

When the second stage of a SpaceX Falcon 9 rocket failed to reach a high enough orbit on 11 July, the 20 Starlink satellites it released were doomed. Within a couple days, the satellites had fallen back into Earth’s atmosphere, burning up as anthropogenic meteor showers.

Although the demise of the 20 Starlink satellites was premature, such fiery “deorbits” are also the preferred way to dispose of spacecraft at the end of their operational lives, so they don’t drift on as space junk. But with commercial plans to put many tens of thousands of satellites into orbit in vast megaconstellations, researchers are starting to wonder about the atmospheric consequences when those spacecraft are retired in large numbers. Recent studies highlight growing concerns over the rising concentrations of metal particles and gases from satellites that can linger in the stratosphere for years, potentially catalyzing the destruction of ozone.

“Almost no one is thinking about the environmental impact on the stratosphere,” says atmospheric chemist Daniel Murphy of the National Oceanic and Atmospheric Administration’s Chemical Sciences Laboratory...

... Concern started to grow when SpaceX began to mass produce Starlink satellites, which provide nearly global internet access to a growing customer base. Today, there are more than 6000 Starlinks in orbit and they represent nearly two-thirds of all operational satellites. SpaceX has applied for permission to launch another 30,000 and other companies are in hot pursuit: Amazon is working on a 3200-strong constellation and China will launch the first batch of a 12,000-satellite fleet in August. If they and others succeed, operators will soon be disposing of nearly 10,000 satellites a year, given the typical 5-year life span of such spacecraft, researchers estimate.

For now, the mass of such disposals is just 3% of the natural input of meteors from space, aka shooting stars, according to a 2021 analysis by Leonard Schulz of the Technical University of Braunschweig and colleagues. But in a future with 75,000 satellites, the injected humanmade mass rises to 40% that of meteors...

... In 2023, Murphy and colleagues reported the first direct evidence of how satellite re-entries are changing the composition of the stratosphere, based on data from a NASA WB-57 aircraft that flew from Alaska to altitudes of 19 kilometers. Using an onboard laser mass spectrometer, they found tiny droplets of sulfuric acid containing 20 different elements that likely came from satellites and rockets, as they were present in ratios that matched those of spacecraft alloys. The amounts of lithium, aluminum, copper, and lead all exceeded the estimated contributions from meteors...