The atmospheric impacts of satellite re-entry.

Summary

Podcast Summary:
T-Minus Space Daily – "The Atmospheric Impacts of Satellite Re-entry"
Host: Maria Varmazas (N2K Networks)
Guest: Professor Min Kwan Kim (University of Southampton)
Date: November 1, 2025

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Overview

This episode explores the atmospheric effects of satellite re-entry, focusing on the release of metals like aluminum into the upper atmosphere and the subsequent implications for atmospheric chemistry and ozone depletion. Host Maria Varmazas interviews Professor Min Kwan Kim, principal investigator of a UK Space Agency-commissioned study, to unpack the risks, uncertainties, and future directions relating to satellite atmospheric ablation.

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Key Discussion Points & Insights

1. Background: Rising Satellite Re-entries and their Impacts (1:34)

• Maria introduces the topic by noting concerns about increased metal content in the atmosphere due to the practice of burning up decommissioned satellites for debris mitigation.
• Early evidence suggests atmospheric concentrations of metals are growing, prompting investigations into environmental safety.

2. The UK Space Agency Study (2:54–4:58)

• Prof. Kim’s team, along with other groups, carried out targeted studies to assess environmental risks.
• Findings were disseminated at a workshop, in conjunction with the Secure World Foundation’s Sustainability Summit.
• Four separate studies contributed: University of Southampton, Durham University, University of Leeds, and private company BESTED.

“With the support with the UK Space Agency, we actually organized the workshop ... to disseminate our findings ... the hope [is] the community can use our research as the foundation for broader study.” — Prof. Kim (4:01)

3. Scope of Prof. Kim’s Research (5:19–6:34)

• The focus was evaluating the risks of the prevailing satellite disposal method—atmospheric re-entry.
• The central question: Is burning satellites in the upper atmosphere environmentally safe, or are we risking significant atmospheric or climate impacts?
• Prof. Kim clarifies: “We don’t want to find the solutions ... basically the risk, what potential the problem can be ... and what is the research gap.”

4. Estimating Ozone Depletion from Satellite Re-entry (7:21–10:14)

• Due to satellite design diversity, a "generic satellite" model was used for risk assessment.
• Key estimate: Re-entry of one satellite could potentially destroy 6–8 tons of ozone.

“Based on our estimation, it is somewhere around six to eight tons for the one satellite.” — Prof. Kim (8:09)

• Larger implication: For a "mega-constellation" (e.g., 10,000 satellites re-entering annually), the effect could be the destruction of 1% of the ozone layer.

“Basically the 1 mega-constellations can impact like 1% of the ocean layer. ... The 1% odor [ozone] layer deflection is ... the 1% increase of the skin cancer rate.” — Prof. Kim (9:40)

5. Lingering Uncertainties and Knowledge Gaps (10:41–12:35)

• Models diverge about how long satellite-borne particulates remain in the upper atmosphere; estimates vary from 4–5 years to 30 years.

“It’s bearing from the 30 years prediction ... to 4 to 5 years prediction ... So still there are some unknowns ... that is the role of the scientist, like me, to improve the accuracy.” — Prof. Kim (11:00)

• The need to better synthesize knowledge from different disciplines remains a challenge.

6. Next Steps: Unifying Industry and Scientific Approaches (14:25–15:57)

• The team is developing generic satellite and scenario models to facilitate shared research and risk assessment.
• Collaboration with industry is essential, but design confidentiality complicates data sharing.

“Our solution is ... let's see the generating some generic satellite without revealing their detailed design ... later they can optimize ... for their actual satellite.” — Prof. Kim (15:57)

7. Which Materials are Worst? ("The Bad Guys") (16:55–18:22)

• Aluminum oxide tops the list of most problematic byproducts, followed by silicon and magnesium oxides.
• Aluminum oxide is stable, but impurities can make it particularly destructive to ozone.

“The problem is not just the aluminum oxide, basically that’s the impurity. Aluminum oxide alone itself is fairly stable. But if there are ... impurities in there, these guys act like ozone badly.” — Prof. Kim (17:51)

8. The "Cooking" Analogy: Why Re-entry Chemistry Is So Complex (18:36–19:42)

• Prof. Kim uses a cooking analogy to illustrate that the conditions of re-entry (i.e., "the recipe") drastically affect what byproducts are formed and their potential toxicity.

“Same satellite, how we burn it, how we cook it—our taste, like a byproduct, is very different. So what we scientists ... try to do is to find the best recipe to minimize those toxic products.” — Prof. Kim (19:21)

9. Policy, Regulation, and the Need for Rapid, Parallel Progress (20:22–21:31)

• The cross-jurisdictional nature of the problem (space law vs. national regulation) poses regulatory challenges.
• There may not be enough time to wait for slow regulatory cycles; action and regulation need to advance in parallel.

“Normally once we find the scientific evidence, we set the regulations ... This takes a really long cycle. But this kind of the problems we don’t have such elegant timeline. So basically we have to do both in parallel.” — Prof. Kim (21:14)

10. Call for Industry and Community Involvement (21:59–24:23)

• Prof. Kim’s team is surveying industry to create representative scenarios and configurations.
• Broader, cross-disciplinary collaboration—including policymakers and regulators—is needed.

“We have to tackle this problem together because this is not just done by the scientists or engineers—also ... policymakers and regulation makers.” — Prof. Kim (23:33)

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Notable Quotes & Memorable Moments

• On the challenge of predicting atmospheric impacts:
  “We call this the known unknown and the unknown unknown—Rumsfeld honors.” — Prof. Kim (10:52)

• On the urgency of developing solutions:
  “We don’t have such elegant timeline ... we have to do both in parallel.” — Prof. Kim (21:18)

• On the need for a shared approach:
  “This is too big a problem solved by one university or solved by one company. ... We have to tackle this together.” — Prof. Kim (23:08)

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Important Timestamps

• Introduction to atmospheric impacts: 1:34
• Study background and dissemination: 2:54–4:58
• Risk assessment and "generic satellite": 7:21–9:28
• Ozone depletion estimates: 9:40–10:14
• Discussion of unknowns and need for models: 10:41–12:35
• Aluminum oxide and other materials' impacts: 16:55–18:22
• Cooking analogy for re-entry chemistry: 18:36–19:42
• Regulation challenges and call to action: 20:22–24:23

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Conclusion

The episode provides a rich exploration of the yet-fully-understood impacts of satellite re-entry on Earth's atmosphere, with a candid discussion of what is known, what remains uncertain, and the complexities facing both industry and the global scientific community. The conversation is an urgent call for joint action, encouraging collaboration across sectors—industry, science, and policy—to better quantify risks and develop responsible mitigation strategies.

For more on contributing to the ongoing studies or to respond to Professor Kim’s survey, contact N2K Space Daily.

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This summary omits advertisement and non-content interludes; all quotations maintain original context and tone.

Transcript

[A]

You're listening to the N2K space network.

[B]

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[A]

When satellites burn up upon re entering Earth's atmosphere, they release particles and gases, including metals like aluminum, which may affect atmospheric chemistry. And this process, known as atmospheric ablation, is still poorly understood. But early evidence does suggest that metal content in the atmosphere is rising. Should we be concerned? Let's find out more. I'm Maria Varmazas and this is T Deep Space. To address the uncertainties around atmospheric ablation, the UK Space Agency commissioned three targeted studies to investigate the potential impacts of satellite reentry. I spoke to Professor Min Kwan Kim from the University of Southampton about his findings. Dr. Kim, thank you so much for coming back on the show. It's been about a year. I really am glad to see you again.

[C]

Yes, it's great to see you again, demaria. So we finished our initial study funded by the UK Space Agency recently and we publicly released our findings recently through the UK Space Agency, the public blog.

[A]

That's wonderful because that is indeed when we last spoke. You were very kind in telling me, listen, wait till it's all released. And so I've been sort of eagerly awaiting the news that it's public now. So here's the here I am very eagerly. I'm a student sitting down going, I really wanna learn. So let's start first with the event at which I think a lot of your work has been recently unveiled. Let's start with that to sort of set the scene when and where was that and what happened there.

[C]

So yeah, so after we finished the study funded by the UK Space Agency, so we produce really long document. It's still over the couple Hundred pages. So that is the detailing all of the our findings. So but we understand it is very difficult to read all of the document. So with the support with the UK Space Agency, we actually organized the workshop to disseminating our findings with conjunction with the Sustainability summit organized by the Secure World Foundation. On the workshop we actually summarizing all of the four studies. So the one is from us, one is from the Dunham University, one is from the University of the lead, one is from the Bested, which is private company. So the workshop is basically the disseminating what we founded and also the hope the community can use our research finding as the foundation for the broader study.

[A]

Excellent, Excellent. So I'm going to narrow the scope because it sounds like there's a lot more conversations I need to have, but I'm going to narrow the scope specifically to what you and your research team, what you all worked on. So please let's review for folks who may have forgotten or didn't listen to our last episode, what were you specifically researching?

[C]

So yeah, so what we doing done through these studies? We study about the risk of the current the practice to disporting the satellite. So we know the space W is the big issue. So to mitigate the space double E problems the international community they have the regulation to de orbiting the satellite within the 25 years recently changed to the 5 years by the the US but the current practice is the best way to removing from the orbit is the atmospheric reentry. The other means is the body. So our study is to basically to start with a simple questioning, is it environmentally safe way if we burn the satellite at the high altitude or the upper atmosphere, could it cause any significant environmental impact? We also have the experience for the global climate changes. So we don't want to make any similar mistake again. So that is our starting point.

[A]

That is quite a starting point. Anything that we should know that was not in scope of this investigation just for our context?

[C]

Yeah. So this is like a very complicated problem. So basically through this study we don't want to find the solutions. So what we want to understand through this study is basically the risk of these problems and what potential the problem can be caused by the this kind of the practice. And what is the research gap we have and what is the direction we have to push this kind of the area into the next level. So that is the main envelope of our study.

[A]

Sounds great. If you don't mind, could you walk me through all of those? I know it's a lot, but I'm sure it's all top of mind for you right now. So walk me through all that because I really am eager to find out.

[C]

So the first we have to understand what is the potential risk of this one. Obviously it is really complicated problems. So we have to simplify situation. Because the problem is every satellite is the unique design. They have the unique. The. The shape, the unique. The. The composition of the material. So we have to.

[A]

Yeah.

[C]

To invent some genetic satellite which is the most popular. So we we using the one satellite and the to estimate. Okay, well if we desaturalize the bond how much the the metal oxide can be produced. And we predicting it is basically the metal oxide is the environmentally toxic by decomposing the ozone. So we estimated how much ozone can be potentially can be destroyed by the one satellite. So based on our very love estimation, it is somewhere around six to eight tons for the one satellite.

[A]

Six to eight tons from one satellite?

[C]

Yeah. So this is not large amount because of the earth has to be quite big.

[A]

Yeah, the Earth is huge. Okay. Yes. Granted. Yes.

[C]

So don't be panicked. So we have plenty of the ocean. So but some of these the constellations. We call this the mega constellations. So they plan to let go 40,000, 50,000. So there's a large number of the satellite and open their lifetime is the four to five years. So literally means the one big mega constellation. They have to burn about the 10,000 satellite annually. So which have the simple mass it is about the 60,000 to the 80,000 tons. It seems like a large number is actually not the large. It's like less than 1% of the oceans can be destroyed. Finding one constellations still.

[A]

Yeah, so yeah I was going to say the scale is hard I think for an average person to wrap their head around because we're talking such massive numbers and amounts. So yeah, thank you for that percentage.

[C]

That's very important easy translations to understand like a normal people. Basically the 1 mega constellations can impact like 1% of the ocean layer. If we have the 2 mega constellations, literally we have the 2% of the order layer deflections. And there are some studies done by the who a while ago. Basically the 1% odor layer deflection is to literally translate into the 1% increase of the skin cancer rate.

[A]

Interesting. Not desirable.

[C]

Yeah. So if it increases 1%, basically it is representing about the thousand souls. Wow.

[A]

My goodness. That's important context. Honestly that's something that you mentioned when I spoke to you last year was also about how long the. I'm summarizing this poorly I apologize how long things remain in the upper stratosphere because that was also. Did your research cover that as well?

[C]

Yeah. So we do some very brief research because of the we first we have to understand why what we what we don't know.

[A]

That's right in the context.

[C]

So we call this the known unknown and the unknown unknown Rumsfeld honors.

[A]

Yes, yes.

[C]

So because of the this area is so complex. So the predictions to how long it takes to reduce the particle coming down is varying from the which model we using it it's bearing from the 30 years prediction from some of the researchers and 4 to 5 years prediction from some of the other researchers including us. So you can get judging one hand is the three decade, other hand is the half decade. So still there are some unknown. So basically that is the role of the scientist like me to improve the accuracy. So this is like a weather forecast.

[A]

So yeah, no this area so much about this. This realm is just completely unknown. So it must be fascinating for you to be studying this frontier frankly of and just learning about something that we've just known very little about.

[C]

So the honestly the community has the good knowledge in related to this area but the problem is that they are not the organized well so this is our first problems from the space the ages. So we have the knowledge from the different area but we didn't concentrate those knowledge to tackle this problem.

[A]

We'll be right back.

[B]

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[A]

So there's a lot of things that we still don't know and I'm sure that that is a lot of what you are thinking about and moving forward. So what is, what is your next step from here? What are you looking at next?

[C]

So basically what we want is that we want to make some genetic case because of the. What we. Ideally what I want is to help all of the community to focus to address these problems. Currently everyone has in their different view different assumptions because of the complexity of the problem. So therefore we want to basically propose some of the genetic scenario with the generic the configuration of the satellite. For that we are consulting with industries so we're just consulting the different industry to say okay this, the genetic. The satellite configurations could be representing your system, your missions. So then we can focus on those. The one simplified scenario to say okay, what happened under this scenario. Whether this is the problem for the next ten years or twenty years or hundred years.

[A]

That's right. Yeah. Mitigation is. Is that. That is the. That is the place where my mind goes is how does one mitigate this? And that is the. We're figuring that part out. Yeah. So I won't ask because I know it's like we're still figuring that out. I'm curious how your discussions have gone with industry so far. What have you been hearing?

[C]

So the actually the industry is the very keen to support these problems. So because of the. The these are they directly related to their operations? So the problem is actually their Lego the design detail. So industry they don't want to rebuild their design detail but they still want to contributing it. So therefore our solution is okay, let's see the generating some generic satellite without rebuilding their detailed design later they can optimize the satellite or tailor the satellite configuration to the actual satellite to predicting their emissions. Our first step is literally consulting with them and to basically configure a generic representative the satellite model.

[A]

Are there certain composites or elements that are maybe more of a problematic? Is aluminum a really big one? Is any. I'm just curious, is there anything that any conclusion we can draw or is.

[C]

That just completely too Basically we we released the Lego some of the top five top ten. We call these the bad guys. So because of that there are many different species. We have the like more than 100 different byproduct. So we have to prioritize okay, which one is the most problematic. So definitely the top one is the Metal oxide, so is the aluminum oxide is pretty much the top one because they are dominated by the mass and the silicon oxide. This is another one. And the another one is like lithium oxide or the mangan oxide, magnesium oxide. The other oxide is not critical. But the problem of the aluminum oxide is not just the aluminum oxide, basically that is the impurity. So aluminum oxide alone itself is fairly stable. But if there are some impurity in there, these guys act like ozone badly, basically.

[A]

Interesting.

[C]

Yeah.

[A]

Huh?

[B]

Wow.

[A]

Oh. So it. There are so many different implications of this. And I'm. I'm just going to be so fascinated to hear how this resonates with a lot of different, not just industries, but other researchers. And because there's just a lot, I'm just thinking material scientists, their heads must.

[C]

Be really, really spinning when I communicate with the public to understand this problem. So I open the explain using the cook. So this problem is very similar to the cook. So I'm not good cook. So when I have the same ingredient with my wife, she's actually good cook. So if I having the same ingredient like a meat, so same recipe, but slightly different way to cook, they have the different taste. For example, if we have the same beef, whether we cook the green like a steak, while we're using the French cooking style like a confit, you can see the taste is very different, texture is very different. So which means same satellite how we bonnet, how we cooking it? So our taste like a byproduct is very different. So what we scientists, like me, we try to do is to finding the best recipe to minimize the dose toxic product.

[A]

So it is to be continued to find out what that recipe is for optimal cooking of the satellite steak. But the work continues. But I'm so fascinated by what you have already found because I have to tell you, I think of all the conversations that I have had, what I have learned from you, I have told to so many people who are not interested in space whatsoever because it affects everybody, it affects our whole planet. And I've had a lot of fascinating conversations with people about, well, what's the difference between a satellite and just a random space rock coming in? It's just like, it's just really interesting hearing those how people are thinking about it. So it's so cool that you're researching this.

[C]

Yeah. And also through the study, we also figured out it is very challenging to set some regulations because of this problem. It's not just in the space, it happened in the ground. So.

[A]

That's right.

[C]

The space obviously governed by the space law, the U.S. the outer space Treaty, if it comes down, it's going to be governed by the individual countries then who going to be setting regulations, how they can be enforcing it. So this kind of the thing is the other kind of the difficulties.

[A]

Yeah, no, yeah, yeah. Regulations are extremely, extremely difficult. Sorry, I didn't mean to interrupt you. I know you're, you're midsole. Sorry.

[C]

So what we understand is the challenge is actually the timing. So normally once we find the scientific evidence, we set the regulations, we implying it we finding the mitigation strategy. This take a really long cycle. But this kind of the problems we don't have such elegant timeline. So basically we have to do the both in the parallel.

[A]

Hmm. It's always when it gets to the implementation phase with a lot of things where it gets very tricky. My sympathies. I'm curious if I recognize this is probably a little out of scope, but a lot of our listeners are in the space industry. So is there anything that you specifically want to tell them, want them to know? I suppose a call to action may be a bit much, but if there is one, if there's anything you want to say to them specifically.

[C]

So basically we try to do some simple survey through the space industry to basically create most representative scenarios and the satellite configurations. So we tried to disseminate in some of our initial survey to basically, okay, this is the satellite, whether it's the representative, your satellite, yes or no. Basically we have these simple questions and also try to create some of the generic scenario to whether it's representing your scenarios, yes or no. So based on that is basically the feedback from the industry, from the academia and the government. We try to basically create most reliable or representative the scenario for all of the industry, all of the people.

[A]

So that sounds like something that maybe we can share with our audience so they can respond to that. Okay, I will make sure that we include that as well. Well, is there anything else that you would like to leave the audience with? Since we're coming up on time, I want to give you the final word. Anything else?

[C]

Yeah, so this we understand this is the problem which we don't know whether it could be problems or not, but this is some of the area we need to having some the support from the community. So the also we have to tackle this one together. So it is the two big problem solved by the one university is solved by the one company. So we have to tackle this problem together because this is not just done by the scientists or engineers. Also need to done by the policymakers and the regulation makers. So once we get the data showing, okay, this is really problems, we literally make some the technology ready. Okay, this is our mitigation, okay, how this is the solve the problem. And we also try to set some small international like a working group or small community basically to the surprise to mutate how we can solve the problem was data exchange. Okay, which model is the better and how we can focus our effort to tackle this problem together.

[A]

Fascinating. Well, thank you Professor Kim. Thank you for sharing your findings with us. This is so fascinating and so important. So thank you. I look forward to learning more as more is learned and please come on back and share. I really enjoy these conversations. Thank you so much for what you do.

[C]

Thanks Maria. And I want to also appreciate my deeply appreciation to the UK Space Agency. So they actually funded this study and they actually supported this problem first in the global level and to basically disseminating this issue to globally.

[A]

That's T minus deep space. Brought to you by N2K CyberWire we'd love to know what you think of our podcast. Your feedback ensures we deliver the insights that keep you a step ahead in the rapidly changing space industry. If you like our show, please share a rating and review in your podcast app or you can send an email to space2k.com we're proud that N2K CyberWire is part of the dark daily routine of the most influential leaders and operators in the public and private sector. From the Fortune 500 to many of the world's preeminent intelligence and law enforcement agencies, N2K helps space and cybersecurity professionals grow, learn and stay informed. As the nexus for discovery and connection, we bring you the people, the technology and the ideas shaping the future of secure innovation. Learn [e-mail] N2K's senior producer is Alice Carruth. Our producer is Liz Stokes. We are mixed by Elliot Peltzman and Trey Hester with original music by Elliot Peltzman. Our executive producer is Jennifer Ibin. Peter Kilpe is our publisher and I'm T minus host Maria Varmazes. Thank you for listening. We'll see you next time. It.