José Pedro Ferreira presents his keynote speech, “Clearing the Air: Understanding and Engaging on Possible Atmospheric Impacts of Space Activities” to an international audience of leaders in the space industry
The setting was a stone’s throw from the Seine, at the Centre de Conférences Pierre Mendès in Paris. But you might have thought we were at a gathering in the International Space Station. The conference hall was filled with senior representatives from national space agencies, researchers from leading academic institutions and the executives of global commercial space companies. They had gathered to assess a topic that isn’t for the faint-hearted: how sustainable is the human presence in space, and how are activities above Earth’s orbit likely to impact life down on the ground?
These are the big questions at the heart of the Summit for Space Sustainability. For the 7th iteration of the Summit, which took place on October 22-23, 2025, the keynote speaker would have been familiar to anyone who spends time in the labs, classrooms, and corridors of the USC Viterbi School of Engineering: José Pedro Ferreira, a PhD candidate in the Department of Astronautical Engineering.
A PhD with the power to impact policy
Ferreira – who is advised by Professor Joseph Wang – researches how space debris interacts with Earth’s atmosphere, and how these interactions inform the design, deployment and governance of space technology. As a Fulbright scholar and NASA doctoral fellow, he’s backed to provide high-impact research, having secured $150k in competitive federal funding.
His keynote speech at the Summit, “Clearing the Air: Understanding and Engaging on Possible Atmospheric Impacts of Space Activities,” proposed a significant pivot when it comes to assessing space sustainability: a shift in attention from orbital congestion and debris mitigation, to assessing the less visible impact of what happens when satellites burn up on reentry to Earth’s atmosphere.
Deorbiting spacecraft at end-of-life is considered best-practice to reduce collision risk and limit the long-term accumulation of debris. But Ferreira’s research underscores a consideration often overlooked in policy discussions. “Sustainability is a lifecycle question,” Ferreira explained. “It doesn’t end when an object leaves orbit.”
When satellites reenter Earth’s atmosphere, they do not simply disappear. Under intense aerodynamic heating, most of their structures – composed largely of aluminum – vaporize, breaking down into smaller particles. “When satellites reenter, they are transformed,” Ferreira explained. “That material is redistributed, therefore interacting with our atmosphere.”
Data to affect change
For decades, the scale of that redistribution was assumed to be negligible. However, recent data suggests otherwise. Ferreira’s research indicates that in 2024, anthropogenic aluminum deposition from spacecraft reentries exceeded the natural contribution from meteoroid dust. That milestone does not establish environmental harm – yet. But it does mark a measurable shift in atmospheric composition that tracks back to human space activity.
As satellite constellations expand and the rate of reentry rises, the cumulative mass of material introduced annually increases. What was once thought marginal may soon become structurally significant.
“This data doesn’t automatically mean damage,” said Ferreira, offering momentary relief for those gathered at the Summit. “But it does mean that our activities are not without consequence, and careful monitoring is necessary.”
A reckoning for international regulation
Current regulatory frameworks have historically stopped at orbital safety. Environmental reviews tend to focus on launch emissions and terrestrial impacts, rather than the atmospheric chemistry of reentry byproducts.
Scientists are still investigating how long anthropogenic metal particles persist in the mesosphere, how they interact chemically, and whether they influence ozone chemistry, radiative balance or high-altitude cloud formation. “There’s a lot we don’t yet understand,” Ferreira acknowledged. “The key point is that we now know enough to take the question seriously.”
That framing is a call for scientific restraint rather than alarm. Detectable compositional change, Ferreira argues, warrants structured investigation – particularly before scaling trends make the phenomenon more difficult to assess.
Space activity, Ferreira points out, does not unfold outside Earth’s environmental systems. It operates within them. As humanity’s presence in orbit scales, so too does its material footprint – including the fraction that returns as vaporized metal. As space activity becomes more commercialized and more internationally distributed, sustainability frameworks must evolve in parallel.
For an international audience of policy makers, this advice hits home. The upper atmosphere is inherently global; atmospheric particles circulate across hemispheres, unconstrained by national borders. “No single country can fully characterize this alone,” Ferreira said. “It’s an inherently international research problem.”
Published on February 25th, 2026
Last updated on February 25th, 2026