Long-exposure photography shows the paths of satellites criss-crossing the night sky. Alan Dyer / VWPics / Universal Images Group/Getty

This story was originally published by Yale e360 and is reproduced here as part of the Climate Desk collaboration.

On a mid-November evening, at precisely 7:12 p.m., a SpaceX Falcon 9 rocket lifted off from Cape Canaveral Space Force Station on the Florida coast. It appeared to be a perfect launch. At an altitude of about 40 miles, the rocket’s first stage separated and fell back to Earth, eventually alighting in a gentle, controlled landing on a SpaceX ship idling in the Atlantic Ocean.

The mission’s focus then returned to the rocket’s payload: 29 Starlink communication satellites that were to be deployed in low-Earth orbit, about 340 miles above the planet’s surface. With this new fleet of machines, Starlink was expanding its existing mega-constellation so that it numbered over 9,000 satellites, all circling Earth at about 17,000 miles per hour. 

Launches like this have become commonplace. As of late November, SpaceX had sent up 152 Falcon 9 missions in 2025—an annual record for the company. And while SpaceX is the undisputed leader in rocket launches, the space economy now ranges beyond American endeavors to involve orbital missions—military, scientific, and corporate—originating from Europe, China, Russia, India, Israel, Japan, and South Korea. This year the global total of orbital launches will near 300 for the first time, and there seems little doubt it will continue to climb.    

“We are now in this regime where we are doing something new to the atmosphere that hasn’t been done before.”

Starlink has sought permission from the Federal Communications Commission to expand its swarm, which at this point comprises the vast majority of Earth’s active satellites, so that it might within a few years have as many as 42,000 units in orbit. Blue Origin, the rocket company led by Jeff Bezos, is in the early stages of helping to deploy a satellite network for Amazon, a constellation of about 3,000 units known as Amazon Leo. European companies, such as France’s Eutelsat, plan to expand space-based networks, too.

“We’re now at 12,000 active satellites, and it was 1,200 a decade ago, so it’s just incredible,” Jonathan MacDowell, a scientist at Harvard and the Smithsonian who has been tracking space launches for several decades, told me recently. MacDowell notes that based on applications to communications agencies, as well as on corporate projections, the satellite business will continue to grow at an extraordinary rate. By 2040, it’s conceivable that more than 100,000 active satellites would be circling Earth.

But counting the number of launches and satellites has so far proven easier than measuring their impacts. For the past decade, astronomers have been calling attention to whether so much activity high above might compromise their opportunities to study distant objects in the night sky. At the same time, other scientists have concentrated on the physical dangers. Several studies project a growing likelihood of collisions and space debris—debris that could rain down on Earth or, in rare cases, on cruising airplanes.

More recently, however, scientists have become alarmed by two other potential problems: the emissions from rocket fuels, and the emissions from satellites and rocket stages that mostly ablate (that is, burn up) on reentry. “Both of these processes are producing pollutants that are being injected into just about every layer of the atmosphere,” explains Eloise Marais, an atmospheric scientist at University College London, who compiles emissions data on launches and reentries. 

As Marais told me, it’s crucial to understand that Starlink’s satellites, as well as those of other commercial ventures, don’t stay up indefinitely. With a lifetime usefulness of about five years, they are regularly deorbited and replaced by others. The new........

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