Rocket soot and vaporized satellite metals represent a massive — and largely unchecked — geoengineering experiment with massive potential planetary downsides.
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Billions of years in the future the Sun will collapse into a “white dwarf” and all known life depending upon it will cease to exist. But even before that happens, the Sun will swell to over 200 times its normal size during a “red giant phase” and engulf the Earth. In short: Should humanity survive the accelerating climate chaos, the looming threat of nuclear war, and the potential rise of super-intelligent (though not necessarily benevolent) AI, death still awaits our species in the end.
For this reason, seeding the cosmos with human settlements has become Elon Musk’s mission in life. “Occupying” Mars would be just the first stop. The bitter irony here is that as Musk and fellow NewSpace billionaires like Richard Branson and Jeff Bezos pour their exorbitant wealth into this colonizing endeavor they are amplifying much nearer-term global damages, and they risk turning the Earth into a sacrifice zone.
These risks were not always so apparent. For the first half-century of the Space Age, rockets erupted from launchpads to deposit satellites in orbit with such infrequency and irregularity that few considered their environmental impact. But as SpaceX and others send those craft skyward with almost clocklike regularity, researchers have begun to study what the impacts of this may be. Their early assessments suggest that this launch frenzy carries potentially profound consequences for Earth’s atmosphere and climate.
“Activities in space are increasing almost exponentially,” said Michael Byers, co-director of the Outer Space Institute. “And every morning brings a new problem.”
Increased access to space has already shown benefits. We’re able to monitor global emissions, improve weather forecasts, and coordinate disaster relief, among other things. Yet even this comes with a cost. As rockets lance skyward and low-orbiting satellites face a fiery demise returning to Earth, they disperse soot and vaporized metals throughout the otherwise pristine upper reaches of the atmosphere. This has caused a subtle and unseen stir in the stratosphere.
The stratosphere ranges from six to 30 miles above the Earth’s surface and houses the protective sheath known as the ozone layer. At ground level, ozone irritates the lungs and airways, causes asthma, and warms the planet. High above Earth, however, it absorbs the sun’s ultraviolet rays, protecting all life. Human activity has weakened this shield before. A global treaty banned the chemicals most responsible for creating that hole, which has only just begun to repair itself. With satellite launches on track to grow tenfold within 10 years at the same time that the ultra-wealthy pursue their plans for space tourism and interplanetary colonization, concerns are mounting that this new space race could undo that progress.
This could increase people’s risk of contracting skin cancer, put yet more pressures on global wildlife, and potentially even reduce crop yields, threatening global food security.
Although the research is still in its earliest stages, scientists have already uncovered enough to warrant caution. Despite this, regulation of the commercial space sector is lax at best. Even as swarms of tiny satellites increasingly crowd the sky, the Federal Communications Commission exempts them from environmental review laws. And the Federal Aviation Administration seems unfazed by SpaceX’s increasing emissions. So, the world lacks any means of addressing what is, in some critical ways, very much an unsupervised geoengineering experiment.
For decades, the cosmos remained the realm of wealthy nations. Launches were expensive and therefore few and far between. Even as they peaked in the 1970s and 80s with roughly 120 per year, spacefaring countries gave little thought to what that might mean for the planet. They worried even less about any harms the satellites orbiting Earth might cause.
This began to change in the mid-80s as attention turned toward the hole rent open in the ozone layer above Antarctica, where extreme cold allowed an atmospheric proliferation of chlorine compounds to dismantle ozone molecules. Concern about that led to the Montreal Protocol in 1987, one of history’s most consequential international environmental agreements. The protocol spurred a crackdown on chlorine-heavy pollutants.
Most of the focus fell on refrigerants and aerosols that released the most troublesome chemicals. But, since chlorine is a key component in solid rocket fuel, “there were people near Cape Canaveral that thought they were going to have an ozone hole over them every time a rocket was launched,” Karen Rosenlof, an atmospheric scientist with the National Oceanic and Atmospheric Administration, told Deceleration.
Research validated those fears. On two occasions in 1996, researchers flew equipment through the exhaust plume of a Titan IV rocket and found ozone had all but vanished for miles around. The effect appeared to last just 30 minutes, however, leading them to conclude the impact was most likely insignificant on a global scale. Although some rockets still use solid fuel, most modern launch vehicles — including SpaceX’s Falcon 9 — rely on a particularly dirty fossil fuel called kerosene. Beyond the obvious implications for CO2 emissions, this fuel carries other concerns as the launch rhythm ramps up.
Kerosene-fueled rockets trail a plume of carbon dioxide and water vapor streaked with soot each time they launch. While most discussion of climate change focuses on carbon dioxide, soot is the bigger worry here. Black carbon, as the pollutant is also called, has a powerful ability to warm the planet, Christopher Maloney, an atmospheric scientist with the University of Colorado and NOAA who studies the space industry’s impact on the stratosphere, told Deceleration. In its first 20 years after being emitted, one pound of soot can warm the planet up to 1,600 times faster than a similar amount of CO2. So although a rocket belches some 300 tons of carbon dioxide, the five to 10 tons of black carbon it spews pose a greater warming risk.
That sooty skyprint is only the first atmospheric impact (to say nothing of the impacts to biodiversity surrounding the launch sites, which often includes threatened and endangered species). Most spacecraft launched today skirt the edge of the atmosphere, where wisps of gas and solar wind buffet them and, over time, alter their path until they plunge back to Earth. Others are high enough that they would remain aloft indefinitely if federal regulations didn’t require them to eventually “deorbit” once their missions end.
They disintegrate as they tumble through the atmosphere, creating an invisible mist of metallic particles dozens of miles above Earth’s surface. For decades, no one thought this would be a problem. After all, meteors burn by the ton up there each day. What harm could come with a few more shooting stars?
The damage comes from a metal that is abundant in a satellite but rare, if not entirely absent, in meteors. Aluminum comprises an average of just one percent of a meteor by weight, but is the most common material in a satellite. The mist created during a satellite’s Icarian plunge reacts with oxygen to form aluminum oxide. This substance, also called alumina, accelerates the reaction between chlorine and ozone, exacerbating the degradation of the ozone layer. As stratospheric concentrations of alumina increase, so too does the risk to Earth’s shield.
Photo credit: Greg Harman / Deceleration News
The hazards posed by soot and alumina will only increase as the pace of launches accelerates. After peaking in the 1970s and 80s, global launches declined to an average of 82 each year between 2008 to 2017. That figure has since spiked, reaching 186 in 2022, 223 in 2023, and 263 in 2024. There have already been almost 120 launches less than half way into 2025.
This growth has been driven primarily by the popularity of large “constellations” of often identical satellites. The global positioning system, for instance, relies on 31 craft. A company called Planet Labs operates hundreds of satellites to map Earth’s surface each day. But now, several companies and startups around the world, including SpaceX and Amazon, have announced plans for “mega constellations,” each one comprised of thousands of satellites assembled to blanket the world with high-speed internet access.
From when Sputnik inaugurated the Space Age in 1957 up until 2020, fewer than 10,000 satellites had been launched. The General Accounting Office, however, expects as many as 58,000 satellites in orbit by 2030, the vast majority of those as internet constellations. OneWeb, an early player, has more than 630 satellites and envisions a network of nearly 7,000. Amazon hopes to launch 3,000 of its own. China has six dozen of the 14,000 slated for its “Thousand Sails” project aloft. All are outdone by SpaceX’s Starlink, which has hurled over 8,500 satellites skyward since 2019. The company has filed paperwork with the Federal Communications Commission that suggests 42,000 Starlink vehicles could one day orbit Earth.
Photo credit: Deceleration News
Launching all this hardware could by some estimates require firing around 1,000 rockets every year. In a paper published two years ago, atmospheric scientist Christopher Maloney investigated what all that soot might mean for the stratosphere. By his estimation, so many launches would litter the stratosphere with 10,000 metric tons of soot every year — roughly what global air traffic emits annually (albeit at far lower altitudes).
All this pollution could, on its own, raise stratospheric temperatures anywhere from one to four degrees Fahrenheit, according to Maloney’s research, but neither he nor his collaborator Karen Rosenlof can yet say what that would mean for climate change.
But 1,000 launches annually is just the beginning of what Elon Musk has planned. In a fireside chat during the 2023 International Astronautical Congress, Musk believes that SpaceX would eventually need to launch their behemoth Starship several times a day, and fulfilling his dream of making humanity a multi-planet species could require as many as 10,000 launches per year. While Starship uses a slightly cleaner fuel than kerosene—liquid methane—these vehicles will nonetheless trail soot in their wake.
“We know that liquid methane is going to produce less soot than kerosene,” said Eloise Marais, an atmospheric chemist at University College London, “but we sort of speculate that it’s probably five times less.”
These impacts are being felt at launch sites in Florida, California, and Texas, but it is the launch site at Boca Chica beach that could become ground zero for some of the worst impacts of Musk’s Mars plans. Already, the SpaceX launch facility has caused tremendous damage to a site sacred to the Carrizo Comecrudo, said Christopher Basaldú, one of the co-founders of the South Texas Environmental Justice Network and a member of the Carrizo Comecrudo Tribe of Texas, and with the Federal Aviation Administration permitting SpaceX to increase from five to 25 launches per year, he fears what this could mean for the future. “The existence of SpaceX itself is an environmental disaster,” he said. “Every day it exists, and every day it expands, is an environmental and ecological disaster.”
Compounding concerns around soot, an effort led by NOAA to study the chemical composition of microscopic particles called aerosols suspended in the middle atmosphere found that 10 percent of them were left behind by satellites tumbling through the sky. “I liken this to finding microplastics in the Marianas Trench,” Rosenlof told Deceleration.
All this pollution could, on its own, raise stratospheric temperatures anywhere from one to four degrees Fahrenheit, according to Maloney’s research, but neither he nor his collaborator Karen Rosenlof can yet say what that would mean for climate change.
Between 2016 and 2022, the amount of aluminum entering the atmosphere rose from around 5 tons per year to just over 40 tons per year. If all of the mega constellations planned for launch actually reach space, the inevitable fall of those satellites could drive that number to 912 tons annually. That’s more than 6.5 times more than what is naturally left behind by meteors. A study published last June suggested that alumina’s ability to trigger reactions between chlorine and ozone could cause “significant ozone depletion,” potentially creating new holes in the ozone layer and increasing the planet’s exposure to harmful solar radiation.
A major reason why no one can yet say for certain what this could mean for life on Earth is because, as a rule, satellites are exempt from environmental impact review. According to a 2022 report from the US Government Accountability Office (GAO), the FCC established a categorical exclusion under the National Environmental Protection Act that freed the agency from conducting environmental reviews for most of its activities, including satellite licensing. The rule allows immense constellations to be constructed without any consideration for their consequences. As the advocacy-focused nonprofit Public Interest Research Group stated quite bluntly in a report last August: “That launching 30,000 to 500,000 satellites into low earth orbit doesn’t even warrant an environmental review offends common sense.”
“We recommend that launches for satellite internet mega constellations are paused until environmental reviews are conducted,” Lucas Gutterman, author of that report, told Deceleration.
In its 2022 report, conducted at the behest of senators Tammy Duckworth (D-IL) and Brian Schatz (D-HI), the GAO recommended that the FCC reconsider its licensing process for large constellations. The agency reportedly agreed with the recommendations and, as of June, had begun to review its rules — though that has not stopped or even slowed any launches.
While an environmental review seems justified, conducting them “would be very difficult right now,” Rosenlof said. The Montreal Protocol was preceded by what she called a 20-year exercise to understand what was harming the ozone layers and how to fix it. “We’re probably at the very beginning of yet another 20-year exercise to try to figure out what the impacts of space debris are on the atmosphere,” she said. “So that’s why it’s kind of scary that they’re licensing these things that we don’t have any way of knowing what they’re going to do — except for we’re basically doing a great big experiment.”
While NOAA has perhaps unmatched expertise and equipment to lead this field of research, recent budget cuts threaten the ability of the agency to respond. “There’s really no one else in the world to fill that resource gap and skills gap,” said Marais.
Still, even with plenty left to understand about the precise nature and severity of the local and global environmental impacts of the growing space launch industry, Basaldú makes one thing clear:
“Obeying Musk is not an option for the future of humanity.”
This story by Syris Valentine was originally published by Deceleration and is part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story. WhoWhatWhy has been a partner in Covering Climate Now since its inception in 2019.
