When satellites reach the end of their lifespans, they fall into Earth鈥檚 atmosphere and burn up. This reentry process is generally considered harmless, but as more and more satellites are launched into orbit 鈥� and deorbited into the atmosphere 鈥� it could begin to have deleterious effects on the climate.
at the US National Oceanic and Atmospheric Administration鈥檚 Chemical Sciences Laboratory and his colleagues used an experiment called the to measure the compositions of hundreds of thousands of atmospheric particles in the sky above Alaska. He presented their results on 13 December at a .
The PALMS instrument sits in the nose of a high-altitude aircraft and allows air from outside the plane to pass through it, measuring particulate matter in the air using a set of lasers. There are two main sources of metals in the stratosphere 鈥� meteoroids and reentering satellites 鈥� and the satellite remains tend to contain aluminium, lithium and other elements and compounds that are not formed naturally on meteoroids.
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About half of the particles in the stratosphere have metals in them, and the researchers found that about one-fifth of those particles seem to have come from satellites and other spacecraft. 鈥淎bout 10 per cent of the particles in the stratosphere contain aluminium alloys from spacecraft, and that鈥檚 an extraordinary number,鈥� said Murphy during his conference presentation.
While this probably isn鈥檛 enough to meaningfully affect the stratosphere yet, there are many plans across the space industry to increase satellite launches significantly in the next decade or so, and that could cause problems. Ice forming in the atmosphere tends to begin around solid particles in a process called nucleation, and the way that these metals affect other particles in the atmosphere could boost that process.
鈥淲e don鈥檛 know anything definite yet, we鈥檙e just starting to think about this, but ice nucleation may be one of the major impacts,鈥� said Murphy. 鈥淵ou could considerably change polar stratospheric clouds.鈥� These clouds can destroy ozone molecules in the polar regions, so seeding more of them could be a big problem.
