"The Space Age has released human-made materials in what we consider a pristine area of the atmosphere."
Satellites and spacecraft are polluting one of the remotest parts of the Earth's atmosphere with alarming quantities of metals, a new study found.
The research, published in the journal Proceedings of the National Academy of Sciences, suggests that dying satellites and falling bits of space junk that are supposed to safely burn up during re-entry are actually significantly changing the composition and chemistry of the stratosphere, a layer of sky that contains most of the ozone.
"We are finding that the Space Age has released human-made materials in what we consider a pristine area of the atmosphere," said study co-author Dan Cziczo, a geophysicist at the University of Purdue, in a statement on the work. "And if something is changing in the stratosphere — this stable region of the atmosphere — that deserves a closer look."
It's too soon to know the effects of this pollution, the researchers said, but it nonetheless adds to growing concern over the skyrocketing space industry's environmental toll.
The researchers flew planes nearly 12 miles up, or about double the cruising altitude of most airliners, gathering data with instruments hitched to the nose of their aircraft to ensure their detections would not be contaminated by fumes.
Metals like lithium, copper, aluminum, and lead — all hallmarks of spacecraft — exceeded the quantities of metals naturally occurring in cosmic dust, they found.
In addition, nearly 10 percent of sulfuric acid particles, which are crucial aerosols that shield the ozone layer, were found laced with vaporized spacecraft remnants. The presence of other more "exotic elements" like the metal niobium, the researchers wrote, are an "unequivocal signal" of heat shields used in rockets.
With all that in mind, Cziczo and his team are confident that meteors are not to blame.
"Scientists recently started noticing that the chemical fingerprint of these meteoritic particles was starting to change, which made us ask, 'Well, what changed?' because meteorite composition hasn't changed. But the number of spacecraft has."
The researchers expect there to be an additional 50,000 satellites in orbit by 2030. Given the already massive Starlink constellations from SpaceX, its ambitious plans to expand their numbers, and its competitors like Amazon looking to follow suit, that doesn't sound like an unreasonable figure.
At that rate, the researchers calculate that up to 50 percent of aerosol particles in the stratosphere will contain metals from re-entrying spacecraft.
"Just to get things into orbit, you need all this fuel and a huge body to support the payload," Cziczo said. "There are so many rockets going up and coming back and so many satellites falling back through the atmosphere that it's starting to show up in the stratosphere as these aerosol particles."
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