Nukes in space? Orbital detector could sniff out warheads

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1:04Welcome back to The Nature Podcast. This week, detecting nuclear weapons in space and how the forest of knowledge is under threat. I'm Nick Poucher-Chow and I'm Benjamin Thompson.

1:26First up on the pod this week, we have a story about a potential way to detect where the satellites in orbit are secretly carrying nuclear weapons. Now, a detonation in the vacuum of space wouldn't have the characteristic mushroom cloud and fireball we see here on Earth. What would happen is that there'd be an initial electromagnetic pulse capable of frying electronic circuits. Following this would be a massive build-up of high-energy electrons whizzing around the Earth. These could strike and damage things like solar panels, potentially rendering military, scientific and communication satellites useless, causing chaos back here on the ground.

2:09Back in 1962, the US conducted a test called Starfish Prime, which saw a nuclear weapon detonated about 400 kilometres above the Pacific Ocean. Within months, and unexpectedly at the time, this event caused roughly one-third of the satellites then in low Earth orbit to fail. This was by no means the only high-altitude test conducted by the US and by the Soviet Union, but the aftermath of this event ultimately led to countries signing the 1967 Outer Space Treaty, which prohibits weapons of mass destruction being put into orbit. Fast forward to today, and tensions are rising around the world, with claims and counterclaims about whether states are planning to sneak a nuke into space.

2:57After all, there are several orders of magnitude more satellites in low Earth orbit than there were back in the 60s. A detonation would be catastrophic. But there's a problem. If a nation had sent up a nuclear device and broken the Outer Space Treaty, how would you know? Well, that's the subject of a paper in Nature this week. Specifically, a modelling study suggesting that satellites carrying nuclear weapons in space would emit a telltale signal that could be detected using another satellite. The author of the paper is Areg Danagoulian from the Massachusetts Institute of Technology in the US.

3:36I caught up with him on the phone about the work, and he explained why it's tough to detect a nuclear weapon-equipped satellite. In general, detecting nuclear weapon is not so trivial because they have radioactive components, but those components are not very radioactive. If you move 50 meters away from them, the signature from a passive nuclear weapon is negligible. You are not really going to detect it. You have to come pretty close to it. So if you wanted to really do this, you would send some kind of an inspector satellite that would come up close to this device. And then it can employ something that is referred to as active interrogation methods.

4:12You shine something at the suspect hoping to trigger a process that would reveal whether it has nuclear weapon on board or not. But that's a fairly hostile thing to do. The other side might think that you are trying to destroy their satellite. So something that is politically much more feasible is, let's refer to them as passive things, meaning that you are not shining anything. Instead, you are trying to use existing processes that are taking place anyway, whether you are there or not. and try to identify processes that are specific to nuclear materials. You're looking at this passive method then, and in your paper you put forward a potential way then to detect a nuclear weapon-equipped satellite.

4:55And it is an indirect method that begins with existing high-energy protons trapped in Earth's magnetic field. Tell me about that. So many of these protons have energies of approximately giga electron volt. We call it GV, giga electron volt. At those energies that are high enough, those protons, when they strike the uranium inside the nuclear weapon that the satellite is supposedly carrying, if it's carrying it, they basically rip this nuclei in pieces. The binding energy of the nuclei, which in general is extremely strong, is nothing compared to the kinetic energy of the protons that are striking those nuclei.

5:31So they shred this nuclei, and they free up lots of neutrons. One proton for the right energy, depending on the circumstances, may generate 14 neutrons, 10 to 14 neutrons. And because there's a lot of protons to start with, in the end you're having an enormous number of neutrons. We're talking about millions of neutrons generated per second. So there's like a multiplying effect when these GV protons interact with uranium. And those neutrons, that's the telltale sign of the presence of uranium on the satellite. And so this signature then of these neutrons is what you put forward in your paper as a potential way to pick up whether a satellite has a nuclear weapon on it.

6:12And the idea is this signature would be picked up by another satellite, a shoebox sized satellite. How would this detection work? Yeah, that's exactly right. The idea would be that you would have a small inspector satellite following the suspect at a few kilometers below. You can design an orbit that would make that possible. And this inspector satellite now is searching for those neutrons. is this inspector satellite does see a statistically significant number of neutrons, and it also has to verify that neutrons are coming from above, not from below, because neutrons are also coming from below, from Earth coming up.

6:49That's the reason why it needs to place itself below the satellite, so that direction of the neutrons itself is another signature. If both conditions are met, then it can conclude that the satellite likely carries a thermonuclear warhead on board. And in this work, then you've modeled a small satellite tracking underneath a suspect satellite. How effective does your modeling suggest this approach might be? So there's two questions. One of them is scientific feasibility. So the purpose of the paper is to show that the physics is scientifically feasible. It also shows that if we take today's existing core technologies, that detection is also feasible.

7:31Core technologies would allow us to build such a device. Now, what the paper does not cover is, is this practical? Is this feasible from point of view of engineering? One thing you do mention in your paper is that actually, this could take quite a long time to achieve. You'd have to track the suspect for quite a while. That's right. We estimate that using one or two such, as you call shoebox size satellites, it would take about one week of data collection. Just to be clear, there's a lot of assumptions that go into this statement? Now, question is, you could also come closer. You could bring your inspector a lot closer.

8:08If you bring it to a distance of a kilometer, and if you make your inspector satellite a lot larger, say you have a constellation of 10 shoeboxes, so to speak, now the measurement times are a matter of an hour. Distance, as we discussed earlier, is a politically charged variable. How feasible is the one kilometer, four kilometer? We cannot answer that question, you know. And I've covered a lot of stories that talk about the atmosphere around Earth. Is there the risk that false positives could be an issue? Because there is this soup of particles flying around our heads. Is there another way that these neutrons could be produced that fools the monitor to say that there is potentially a nuclear weapon there?

8:48I spent quite a bit of time running simulations specifically looking for possible false positives and possibility of, say, atmospheric neutrons appearing like a neutron coming from the satellite And we found that essentially the probability of that is negligible, less than 1%. But yeah, false positives are possible. So what it probably means in the real verification scenario, a single measurement would probably not be sufficient. You would want to do multiple complementary measurements. For example, right now, my research group is working on an idea of using those protons to radiograph satellites.

9:23And if there is a satellite carrying a nuclear weapon next to you, you should see that no protons are able to come through it. So we're working on multiple different ways of achieving this verification so that you don't have to rely on a single method's blind spots or false positives. This is a modeling exercise. And as you say, you do make some assumptions in your modeling. I think you say that the nuclear device that the satellite contains has about 95 kilograms of uranium. And one could imagine that warheads can differ right can be heterogeneous and also i suppose if someone were to send up an illicit nuclear device you can imagine they would do their very best to conceal it potentially shielding against any of the neutrons being released that you were saying could be detected given that there is this heterogeneity and this range of what could happen what practical value do you think this paper has why is this paper important do you think Yeah, we don't know how much uranium there is on a thermonuclear weapon, how much fissile material, because it's highly classified.

10:27But what we do know, we have some open public domain information about approximately how much a thermonuclear weapon weighs, okay, because of public disclosures as part of treaties and whatnot. And that tells us that the amount of uranium is likely to be in hundreds or hundreds of kilograms. Okay. That said, as I said, the feasibility study, you know, you can take the result of the feasibility study. Let's say you are doing classified research at atomic weapons establishment, and you know the exact amount of uranium. You can take this result and you can scale it down or scale it up the signal based on what you know is the amount of uranium, which I don't know, but they do know.

11:10Right. So basically, many of the numbers that we use in the paper are essentially kind of placeholders. You can change them and adjust the conclusions accordingly. Now, let me talk about the shielding. You are absolutely right. Shielding would significantly reduce the signal. What it will translate to is that you would require a bigger detector. So maybe instead of detecting that the size of a shoebox, maybe you need to have a satellite that size of a conventional meter by meter or two meter by two meter satellite, which I think is quite doable. And finally then, Arag, your paper is out now. Where does this go?

11:42What are you hoping folk get from this when they read it? Unfortunately, most of the research in this area is highly classified. But the goal of this paper is sort of to excite other people into looking at this and thinking about this method, possibly building such devices. You know, we may do this work for five years and find out that, you know what, this is too hard. Even if it's feasible scientifically, it's not feasible from point of view of engineering. But we should at least try and try not just this other ideas as well that hopefully other people will generate so that ultimately five years from now or 10 years from now we have an actual solution to this problem areg danagulian from mit there to read his paper look for a link in the show notes coming up as languages disappear much of what is known about the amazon could also be lost right now though it's time for the research highlights with katrina clark

12:37Bizarre ice-like domes made of carbon dioxide and water dot the seafloor in one part of the Indian Ocean. These solid mixtures of gas molecules and water are called hydrates. Domes made of methane are common, but while surveying the seafloor to investigate the effects of an underwater volcanic eruption, researchers discovered more than 120 carbon dioxide hydrates. These hydrates were found off the coast of the island of Petite Te in Mayotte, between Madagascar and the southeast coast of Africa. The gas is probably bubbling out of magma beneath the sea floor, and the hydrate domes reached heights of up to five metres.

13:17In some cases, carbon dioxide burbles out of the top of the mounds, rising upwards as milky white droplets. Some researchers have proposed sequestering carbon dioxide in hydrates to reduce atmospheric greenhouse gas concentrations. The new found hydrates provide an opportunity to study how carbon dioxide behaves in these formations. Dive into the journal Nature Geoscience to read more. The genome of the tree sloth species Colipus didactylus hints at how it lives life in the slow lane. Tree sloths are Earth's most sluggish mammals. They spend their lives hanging from trees, moving only to eat, mate and poo.

14:01Their natural metabolic rates are the lowest of any recorded in mammals, but the genomic basis of their evolutionary adaptations is poorly understood. To find out more, a team of researchers sequenced the genomes of Colopus didactylus and a sloth relative, the collared anteater. These sequences were then compared with the genomes of two other sloth species and another related animal, a species of armadillo. The analysis revealed that the tree sloth genomes were loaded with working copies of genetic elements called retrotransposons. These are able to make copies of other genes, which can then take on new roles.

14:37In the tree sloth, many of the genes that had been duplicated were involved in the workings of mitochondria, cells energy factories, and in metabolism, hinting at clues to sloth's slothfulness. Make your way, slowly, over to BMC Biology to read that paper.

14:59In the Amazon, indigenous knowledge of the plants and services they provide, such as food and medicine, is under threat. Now this is down to a range of factors, but a new nature study looks at two together that you may not have thought of. Climate change and the loss of languages that these people speak.

15:23This is the sound of Tikuna, one of the hundreds of indigenous languages of the Amazon basin, a large region in South America that is mostly covered by the Amazon rainforest.

15:38Here, the speaker, Armando Nascimento from the Tikuna Indigenous Group, is describing the respect his community has towards nature. and while the tikuna language currently appears to be stable it's used in homes and schools by many people that's not true of a lot of indigenous languages many of these languages more than half in fact are endangered their risk of disappearing by the end of the century and this is as a result of ongoing pressure from european colonizers and the languages and institutions they have brought with them. And with the disappearance of these languages, knowledge may also be lost.

16:17A language is essentially an index to the forest. This is Rodrigo Camarolet, a researcher who studies human relationships to plants and one of the authors of the new Nature Study. He's previously studied how the loss of indigenous languages would impact medicinal knowledge. In previous work, we found that losing languages will have critical repercussions on the livelihoods of these communities that still rely strongly on their surrounding forests for their livelihoods. Rodrigo and his colleagues showed that a lot of knowledge about plants is tied to specific languages. There are some things that are only known in that language and cannot easily be translated.

16:58That means a lot of knowledge about medicinal plants is under threat if languages are lost according to their analysis. This is not the only thing threatening these people's livelihoods though. It's well understood that climate change will have a substantial impact on the Amazon and the plants that live there, especially when combined with ongoing deforestation. But how this will interact with language loss and how it will affect indigenous communities directly hasn't been studied. Most studies that have explored what will be the fate of biodiversity under climate change have done so by looking at organisms regardless of their importance to local and indigenous communities.

17:42So we wanted to better understand what will happen to those plants that matter to people. In their work Rodrigo and the team wanted to look at the impact that the dual threats of language loss and climate change could have on the knowledge of plants in the Amazon. They started by cataloguing important plants used for food, construction, cultural practices or that have medicinal properties. The loss of plants like these is something that worries Armando. It's a worrying process because it undermines the system of mastery of ancestral knowledge,

18:19as well as losing of homes and traditional footpaths, traditional medicine

18:30and shortages of culturally significant food.

18:44To catalogue the impacts of such a loss, Rodrigo and the team found more than 90 ,000 reports of services being provided to people by plants, by scouring more than 700 references from 1504 to 2023. You are never satisfied by the amount of data you can obtain, but I think we did a relatively thorough job covering references from the 16th to the 21st century. This thorough job allowed them to discover that there are about 5 ,800 plants that are used by indigenous people, which is around a third of known plants that produce seeds in the Amazon, along with a smattering of ferns. The team then wanted to see how these plants might be affected by climate change so they looked at how three different climate scenarios would play out by 2060 to 2080.

19:33One best case scenario was where climate targets are achieved by mid-century and warming would be limited to around 1.8 degrees by the end of the century. They also looked at a scenario with minimal action where there would be more than 3 degrees of warming by the end of the century and they looked at an unlikely worst case scenario where emissions would increase substantially and warming would reach 5 degrees by the end of the century. To put that in context, current projections have the world warming to around 2.6 degrees by the end of the century. With these scenarios in place, the team investigated how they would affect the plants people use.

20:10Not too surprisingly, climate change would lead to a loss of plants and the services they provide. In the best-case scenario Rodrigo and his colleagues looked at, they found that 28 % of plants would go locally extinct. And in the worst-case scenario, they found that 34 % would go locally extinct. But despite the differences in scenarios, one thing was consistent throughout. Regardless of the emission scenarios or these possible futures, we found a consistent trend in that plants that matter to people or utilize plants will be more affected by climate change than plants that are not used by people.

20:51Exactly why this is isn't fully clear. The team found that the plants that people use tend to be distributed across bigger areas, something that Rodrigo thinks may make them more vulnerable to climate change. In any case, the team's analysis suggests that climate change is not great news for the plants that people use in the Amazon basin. But then the team also looked at how losing languages could interact with this. It's estimated that 55 % of languages spoken in the Amazon basin are threatened, meaning that they could go extinct by the end of the century. If this happens, the team project that 26 % of all indigenous knowledge, the knowledge about what plants can be used for, could be lost.

21:30They suggest that this may even be at least as fast as the loss of plants due to climate change. And it's likely that even more will be lost, as we don't know how many more languages there might be that are quietly disappearing. So because in indigenous communities, knowledge is transmitted orally, we can imagine that these indigenous knowledge networks would be analogous to, say, our books. But we don't know when these books may vanish or may burn because with indigenous societies, there's no physical component to see that something is being eroded. The extinction happens in silence. Now, this loss of knowledge is a worst-case scenario, that it seems that no knowledge is maintained elsewhere as the languages disappear.

22:19But when combined with the impacts of climate change, Rodrigo worries that much of our knowledge about plants may disappear, along with the plants themselves. We would never know what we might lose if this were the case. Armando, too, worries about what such losses would mean to his community. It is very worrying to me as someone living within the community.

22:51Because mastery of the mother tongue is a tool for personal, cultural and territorial identity.

23:12As well as for the ancestral knowledge our grandparents have taught us in the various Molokkas of the Tikuna people.

23:32Despite the worries that the knowledge of his people will slowly disappear, including that that has been passed down through generations in the communal houses or malakas of his people, Amando is still optimistic about the future. Rodrigo too is optimistic and sees this paper as a call to action to stop the erosion of knowledge This information we call the forest of knowledge database it is our hope that it will trigger efforts to restore biocultural heritage in the Amazon and for example inform restoration approaches strengthen cultural revitalization efforts that are being developed by indigenous and community-led efforts and also to promote or make available this rich wealth of plants that hopefully can also strengthen the social bioeconomy in the Amazon, which is a key longing for many indigenous and local communities who want to be able to remain in their lands while developing their bioeconomy in ways that are culturally appropriate.

24:52Always I will be optimistic about Mother Nature and always thinking about a successful future.

25:02Where my community's youth and children carry forward their cultural traditions in a healthy coexistence of technology.

25:16That was a man del nascimento of the Tikuna people. He lives in Colombia. You also heard from Rodrigo Camarolet from the University of Zurich in Switzerland. For more on that story, check out our show notes for some links. And that's all for this time. If you want to stay in touch, you can reach out to us on email, podcast at nature.com. or we're on social media at Nature Podcast. I'm Benjamin Thompson. And I'm Nick Petrich Howell. Thanks for listening.

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