UNPRECEDENTED STARLINK REENTRIES: Last month, more than 120 Starlink satellites fell out of orbit. The daily rate of reentries is unprecedented and might be altering the chemistry of Earth’s atmosphere.

 What goes up, must come down–which could be a problem when you’re launching thousands of satellites. Since 2018, SpaceX has placed more than 7,000 Starlink satellites into Earth orbit, and now they are starting to come down. In January alone, more than 120 Starlinks deorbited, creating a shower of fireballs.

“The sustained rate of daily reentries is unprecedented,” says Jonathan McDowell, an astronomer at the Harvard Center for Astrophysics who tracks satellites. “They are retiring and incinerating about 4 or 5 Starlinks every day.”

Planners have long known this would happen. First generation (Gen1) Starlink satellites are being retired to make way for newer models. “More than 500 of the 4700 Gen1 Starlinks have now reentered,” says McDowell.

When Starlinks reenter, they disintegrate before hitting the ground, adding metallic vapors to the atmosphere. A study published in 2023 found evidence of the lingering devris. In February 2023, NASA flew a WB-57 aircraft 60,000 feet over Alaska to collect aerosols. 10% of the particles contained aluminum and other metals from the “burn-up” of satellites.

Right: NASA’s WB-57 high altitude airplane. [more]

What we’re observing is a giant uncontrolled experiment in atmospheric chemistry. The demise of just one Gen1 Starlink satellite produces about 30 kilograms (66 pounds) of aluminum oxide, a compound that eats away at the ozone layer. A new study finds these oxides have increased 8-fold between 2016 and 2022, and the recent surge is increasing the pollution even more.

On the bright side, each reentry produces a beautiful fireball–and the odds are increasing that you’ll see one. Visit the Aerospace Corporation for reentry predictions, and submit your photos here.