Just over a year ago, the upper stage of a SpaceX Falcon 9 rocket plummeted back to the ground after delivering 23 Starlink satellites to low-Earth orbit.<\/p>\n
It was a routine mission, one out of hundreds of rocket launches<\/a> that have delivered just shy of 10,000 broadband-beaming satellites total into space \u2014 and it belched a massive cloud of lithium and other pollutants roughly 62 miles over Europe upon its uncontrolled return, as scientists detailed in a new paper<\/a> published in the journal Communications Earth & Environment.<\/p>\n Researchers have grown concerned about the environmental impact on our planet\u2019s upper atmosphere as satellite launches become increasingly common. It\u2019s not just SpaceX; several other<\/a> companies<\/a> and governments<\/a> are planning to launch their own satellite constellations. Worse yet, the satellites have a limited shelf life<\/a>, which means we\u2019ll be required to keep launching their replacements ad infinitum \u2014 in traffic that appears to be unintentionally pumping the atmosphere full of chemicals.<\/p>\n Rocket launches seem to be injecting metals and other pollutants into the atmosphere as they enter space and make their return. Using a resonance lidar in Germany, for instance, the international team of researchers observed a massive lithium plume from the uncontrolled reentry of the previously mentioned SpaceX rocket in February 2025 at an altitude of 62 miles west of Ireland.<\/p>\n SpaceX\u2019s rocket bodies are made of a special aluminum-lithium, an aerospace-grade alloy that reduces weight. Reentry heats up this material, causing it to break down.<\/p>\n The team claims it\u2019s the \u201cfirst measurement of upper-atmospheric pollution resulting from space debris re-entry and the first observational evidence that the ablation of space debris can be detected by ground-based lidar.\u201d<\/p>\n It\u2019s important to note that there\u2019s a lot we still don\u2019t know about the long-term effects of these pollutants. But given how many rocket parts are expected to reenter the Earth\u2019s atmosphere, it\u2019s certainly worth exploring, they argue.<\/p>\n \u201cThis finding supports growing concerns that space traffic may pollute the upper atmosphere in ways not yet fully understood,\u201d the team wrote in its paper. \u201cContinued growth in satellite launches and re-entries may lead to cumulative effects, with implications for long-term atmospheric composition and climate interactions.\u201d<\/p>\n To experts, it\u2019s a particularly concerning finding considering the possible implications for our planet\u2019s ozone layer, a protective layer of gas ten to 25 miles above the surface that absorbs the vast majority of harmful UV radiation from the Sun.<\/p>\n A 2024 study<\/a>, for instance, found that satellites could equally be injecting harmful pollutants<\/a> such as aluminum oxides into the upper atmosphere as they burn up during reentry.<\/p>\n But the sheer scale of a Falcon 9 upper stage alone, which measures up to 46 feet in height, has experts concerned. Leibniz Institute of Atmospheric Physics professor Robin Wing, coauthor of the latest paper, put the amount of lithium into context, telling the BBC<\/a> that small meteors deposit around 50 to 80 grams of the element a day naturally.<\/p>\n \u201cSo, a single Falcon 9 rocket has about [66 pounds], so this is quite a lot more,\u201d he said. \u201cOur largest concern is aluminium and aluminium oxides interacting with the ozone layer.\u201d<\/p>\n But for now, the exact implications on the atmosphere\u2019s ability to control the climate and temperature remain unknown.<\/p>\n \u201cThis is a new scientific field,\u201d Wing told the BBC. \u201cIt\u2019s hard to speculate because it\u2019s changing so quickly. I hope that if we start our measurements now, perhaps we can get ahead of the curve and identify any potential problems before they become serious.\u201d<\/p>\n