> "The environmental impacts from the reentry of satellites are currently poorly understood," the researchers note in their paper. "As reentry rates increase, i

> "The environmental impacts from the reentry of satellites are currently poorly understood," the researchers note in their paper. "As reentry rates increase, it is crucial to further explore the concerns highlighted in this study." In other words, they have no idea what effect, if any, some extra aluminium oxide is having on the ozone layer. Fun to play follow-the-citation though: > Dominant drivers in re-entry destruction are NO (nitrogen oxides) and chlorine emissions. Other re-entry elements play a negligible role. https://indico.esa.int/event/321/contributions/6403/attachments/4335/6538/esa-csid-21-bekki.pdf https://indico.esa.int/event/321/contributions/6403/attachme... > The results of the present study lead to the conclusion that deorbiting space debris has very little impact on stratospheric ozone https://apps.dtic.mil/sti/pdfs/ADA414310.pdf https://apps.dtic.mil/sti/pdfs/ADA414310.pdf A couple good pull quotes from the simulation study itself: > The chlorine activation reaction is catalyzed on the surface of aluminum oxide particles, with a reaction probability of 2% that boosts ozone depletion > Concerning the future mega-constellations scenario, the worst-case estimation of Organski et al. (2020) is taken The upshot here is that aluminum oxide, where present, negligibly but measurably increases the breakdown of ozone by catalyzing chlorine, where present. Keeping chlorine levels in the atmosphere low is an imperative, and one of the overall success stories of international environmental cooperation. A bit of alum is not going to move the needle, it's entirely inert to ozone chemistry on its own, and a poor catalyst of breakdown in the presence of chlorine. If enough satellites broke up in the atmosphere to provide an atom of aluminium oxide for each chlorine atom, which won't happen, that would lead to a maximum of 102% ozone damage from a baseline of 100%, if every one of those atoms collided with a chlorine molecule, which is also very much not how gas phase chemistry works. So yeah, great study. Seems the satellites are worth the nonexistent risk to ozone that they don't pose. Glad someone checked!