Tracking falling space debris via sonic booms, and getting drunk off your own microbes

This podcast is supported by the Icahn School of Medicine at Mount Sinai, an international leader in research, education, and patient care. The Medical and Graduate School is part of the Mount Sinai Health System, one of the largest academic medical systems in New York City. Ranked among the top recipients of NIH funding, researchers at Mount Sinai have made breakthrough discoveries advancing the health of patients. Here, clinicians and scientists push the boundaries in cardiology, cancer, immunology, neuroscience, genomics, geriatrics, environmental medicine, and artificial intelligence. The Icahn School of Medicine at Mount Sinai. We find a way. This is a science podcast for January 22nd, 2026. I'm Sarah Crespi. First this week, stories from new senior biomedicine reporter Jenny Smith, including one on autobrewery syndrome, where microbes inside the human gut make too much alcohol, how doctors can use the Mexican biobank to guide treatment, and preliminary findings that surgery on the brain's plumbing showed promise for Alzheimer's disease. Next on the show, it's tough to calculate when and where deorbiting spacecraft might enter the upper atmosphere and eventually land. Researcher Benjamin Fernando showed that sonic booms created by fast-moving space debris shake seismic sensors, giving clues to angle of reentry, breakup dynamics, and final destination. Now we have Jenny Smith. She's our newest full-time news reporter here at Science, and she's going to share some of the recent stories she's worked on. Hi, Jenny. Hi, Sarah. Welcome to the podcast. Hi. Hi. Well, a few of these actually I saw coming across the lineup, and I was like, oh, this looks so fascinating. I really wish we could fit it in the podcast. We're going to dig up a few of those from the last couple of months, and we're going to talk about your most recent story, which is on these interesting results out of the Mexican Biobank. This is a biological repository that represents all parts of Mexico. Can you tell us a little bit more about this database? It's very interesting. The Mexican government, back in the early 2000s, commissioned a sampling study across all 31 Mexican states and got into a lot of rural areas. It wasn't meant as a genetic study at that time. They were actually looking for things like prevalence of hepatitis and whether or not public health messaging was working. So they were taking health data, they were taking blood samples, but they were not specifically looking at genetics. What they had the foresight to do was bank 40,000 samples. And that's amazing because a lot of times you see this focus on cities like Mexico City has a ton more genetic data. And of course, Mexico has a lot of diversity. That's what this study is all about. So in 2023, this group published its first genetic study from the Mexican biobank. They actually were able to answer a lot of questions about populations and migrations. And, you know, so fascinating things came out of that study from like a historical and anthropological perspective. But what they always wanted to do, this group of folks working with the Mexican government was see if there were medically relevant genetic findings that they could sort of map onto what they learned about the population. So this next study published in Nature Medicine, palmed in on a couple of them. One is a gene that gives you an adverse response to statin drugs. These are cholesterol-lowering drugs. Right, that a lot of people in Mexico take. They looked at people who have a gene that can produce side effects when you take a statin. They also looked at a gene that makes you susceptible to fentanyl. So that means that if you're a pregnant woman having a C-section or any type of surgery, you may easily be overdosed. Oh, interesting. With fentanyl, it would increase sensitivity. So the idea here is to map it onto populations. They have this gene in different concentrations in different parts of the country, like Yucatan, Mexico City. They're different enough where this actually means something for public health or for clinical visits. Yeah, I think that's the novelty there, right? Mexico has a ton of indigenous groups. Not everybody knows that they have heritage from one or another indigenous group. And yet that heritage in effect dictates your likelihood of having one of these genes that gives you susceptibility to one or another of these medical problems. So it's a really important proof of concept that these genetic studies matter for public health. And so how do you use that in practice? The idea is not to genotype everyone because that's not necessarily affordable. The idea is to say to doctors in a place like Chiapas, this variant has 15% prevalence or frequency in this population. So keep an eye out for this side effect. It's actually very simple. And they created a tool that lets doctors look this stuff up. Usually it's like hospital geneticists and researchers and stuff mining these gene banks. But in this case, it's really intended for regular physicians. Let's move on to another study. This is pretty recent. This is on auto brewery syndrome, which is a rare condition where your gut microbes make too much alcohol. Basically, they ferment the carbs that you eat and it makes you drunk. This is rare, as I said, but it's been documented for over a century. What are some of the consequences of your microbes making you drunk? For one, you can get in trouble with the law. Right. You can lose your job. You can have your family members not believe you and you can have your doctor. not believe you. There is no diagnostic code for autobrewery syndrome. It's rare enough that usually there's a diagnostic odyssey for anybody who comes in. There's a gold standard for diagnosis for this, which is that a person has to be isolated in a clinical setting with no access to alcohol. Like a locked room mystery. Like how is the alcohol getting into this person? Yeah, exactly. We just gave them bread and here they are. Exactly. Here they are. And then they are administered an oral glucose challenge. After some period of time, your blood alcohol level or breathalyzer will be positive, and that's how it's diagnosed. But most people to get to that point have had just terrible family situations and odysseys. The treatment for this is usually avoid carbs, take antibiotics, but it's not super effective. This new study kind of looks in more detail at who in the microbiome is doing this. What did they figure out? You have to step back a little bit. There was a really breakthrough study in 2019 by a Chinese team that's probably done more than anyone to really tease apart auto brewery syndrome. And they had sort of an index patient who was a young man who was drinking Coca-Cola quite regularly. And at one point, I think he was hospitalized with the equivalent of 15 shots of whiskey or something. Oh my gosh. Yeah, yeah. No, it was terrible. What this very clever team in Beijing did was look more exhaustively at his gut microbiota. They found that it was composed of 20% of a Klebsiella pneumoniae strain. It's, you know, not an uncommon bacteria in anybody's gut that is naturally high alcohol producing. 20% of your gut flora being occupied by this one species of bacteria is a pretty startling thing. They took it from this young man who also had fatty liver disease as a result of his constant alcohol exposure. And they put it in mice and gave them fatty liver disease. So that was a very important proof of concept that this bacteria when ingested actually by the mites and allowed to colonize their guts produced this They only had a cohort of about five individuals in that study The new study that we recently wrote about had 22 individuals and it was a first study with healthy controls that were recruited from the same household as the affected person. So they could then exclude environmental confounding causes. What did they find that was different though, was that E. coli was the culprit alcohol producer in a lot of these cases. Now that one, most of us have heard about, and it is common in the human gut. Exactly. That's not his normal job as far as I know. It does create alcohol. Normally we all create some alcohol in our guts, but our liver easily metabolizes it and it's not clinically relevant. And so, you know, what you're saying is you're getting at the essential question here is why does this happen to some people and not others? People living in the same house. And we know from kind of the early microbiome studies that you do kind of share this flora with your family. Why is it only certain people that are getting overgrowth and that overgrowth is leading to not only sometimes drunkenness, but liver disease? They were measuring the gut microbiota during flares of the disease because this is a relapse-remitting disease, a relapsing-remitting pattern. So you have flares. You're not constantly experiencing this, thank God. And they found that those E. coli levels were corresponding to flares. It's a real addition to what's known about this. Does it tell us anything about the mechanism that kind of differentiates these people? No, but the Chinese group has done a lot of work on that. And there's an important link to actual alcohol consumption, which can seemingly prime you for this. Other people, it's more obvious they may have short bowel syndrome or they may have Crohn's disease. They have a known intestinal issue that could cause a dysbiosis. But again, lots of people have all of these things. Right. They do not develop autobrewery system. It may also have to do with how people metabolize alcohol. So what are the next steps? Are they going to try to use this to inform treatment? This study was the second case in the literature in which fecal microbiota transplantation has been used as an attempted treatment of autobrewery syndrome. And, you know, FMT, it sounds simple, you know, you're swallowing capsules, but it's actually not that simple. Your gut flora is basically eradicated with drugs and with essentially like colonoscopy prep type measures. And then you're bombarded with another person's gut flora. In this case, they had to do repeated rounds of it, but it does seem like it provided relief. These patients are not easy to treat. Zero carbohydrate diets are standard. You're not feeding the ethanol producing microbes. And yet, even with that, people have a terrible time with this. So it does look as though FMT is promising and now the same group out of University of California, San Diego that ran this study and also a Harvard group are doing a clinical trial of FMT in people with autobrewery syndrome. All right, last one we're going to touch on. This is on the brain's plumbing, the so-called glymphatic system. Researchers have spent about a decade since its discovery characterizing the system, and now they're starting to look into its relationship with brain illnesses and how it might be tweaked to treat them. Jenny, can you first get us up to speed on the glymphatic system? What is it? So the glymphatic system, so glymphatics refers to bleal cells. Bleal cells, yeah. It's a brain immune cell and lymphatics, obviously. So lymphatic system, I mean, it was not believed or understood that any sort of lymphatic clearance was occurring in the brain or even in the meninges, the membranes surrounding the brain until 2012 and 2015, respectively when these two systems were discovered. So all of this stuff, advanced imaging makes all of this possible, right? The system was suspected to exist for like a century or longer, but really only with, you know, imaging technology has it been proven to exist. This is kind of thought of now as a clearance system, like the way lymph system kind of clears out the rest of the body. But this one is for the brain and it was suspected, but not detected for a very long time. We're talking about cerebral spinal fluid, right? CSF, right? That comes into the brain, mixes with interstitial fluid, which is released by the cells and then it's removed from the brain by way of the meningeal lymphatic vessels, which are so tiny that they weren't really discovered until 2015. So the channels that comprise the lymphatic system are like little micro channels held in place by astrocytes around blood vessels. So the actual natural vasomotion, the dilation and contraction of blood vessels that occurs in a sort of rhythmic constant pattern is what pushes the fluid through. So it kind of rides on the vascular system. So why is it important? It's important because it is the clearance mechanism, as more recent studies have shown, for disease proteins and Alzheimer's and Huntington's disease and a lot of other things. So then the question is, you know, 10 years later, more than 10 years later, people are starting to intervene and starting to see if the lymphatic system can be manipulated to work better. So if it's not working very well, we're going to get a buildup of things that we don't want in there, be it these like products of Huntington's and Alzheimer's, or is it just we can make it work better and maybe clear things faster? Well, it naturally starts to decline with age. So you're at that disadvantage anyway. And if you have a disease process, the combination of less functional glymphatics as you age plus disease proteins could be problematic. There are a number of routes that the researchers are trying to manipulate this with. And drugs is one. What is being tried in that arena? With the drugs, there's a number of strategies being tried. One is an antipsychotic drug that happens to have an effect on aquaporin-4, which is a water channel protein that's active in the astrocytes. It essentially gives glymphatic channels their structure. When it gets all scrambled up, which it can in the case of traumatic brain injury, things don't pass through as well. That's one experimental intervention. Another one involves vasodilation or vasoconstriction. So you can manipulate that with carbon dioxide. You can manipulate it with beta blockers. So there are lots of different interventions being tried to sort of jog the system. So just think about these like channels of water kind of opening up and closing up because you're getting drugs involved. That's right. And that's been tried for traumatic brain or what is that intervention aimed at? A lot of the animal models are traumatic brain injury that they're testing this stuff in Because the same processes that govern fluid clearance and disease protein clearance from the brain also govern brain homeostasis in general, but also, you know, the transport of water out of the brain. And so a lot of the experimental models are looking at brain trauma or spinal trauma and seeing if they can improve clearance and keep fluid from building up. There are also surgical interventions in trials, which I was kind of surprised. That was my starting point for this story is that a brain pathologist that I'm friendly with passed me a description, and it was in a psychiatric journal, of surgeries being done in China that purport to improve meningeal lymphatic clearance. So essentially, it's the same system. You have the glymphatic system sort of inside the brain tissue and meningeal lymphatics that push it out of the brain into the lymphatic system and eventually into the blood. And they being done in Alzheimer patients specifically In humans humans we skipping the whole animal model yeah Is to you know really improve that flow By connecting them By connecting them It a deep cervical a deep neck, limb vessel to a vein. Wow. So it's a type of bypass surgery. Now, it sounds crazy. It has been heavily promoted by one Chinese surgeon who pioneered the procedure, but then it started to attract a lot of interest, including outside of China. So this same doctor was invited a few years ago to the Cleveland Clinic to demonstrate, you know, his procedure and show slides. And a number of trials have been done in China in which it is claimed that people have remarkable improvements in Alzheimer's pathology and symptoms. Right. So not just we see a marker going down, but they're doing cognitive testing that says this person is not declining or is improving. Right. And the cognitive improvements can be rather quick. Some people find that suspiciously quick. There's a few things going on here. It really could be that improving clearance from the meningeal lymph nodes into the body does something else in the brain. In other words, it's not because you're increasing the flow of disease proteins out of the brain, but maybe you're doing something else. But at any rate, it's being taken seriously enough that a large clinical trial is also, when I say large, I don't mean it's necessarily large, but, you know, well-designed clinical trial with animal studies is being designed in the United States. That'll be done out of Yale. So I was intrigued by that just because the studies to date, they're open label studies. I do think it's premature to completely dismiss this. So we got to kind of wait and see on that. That's super interesting. Thank you so much, Jenny. It's been fun talking. Oh, it was my pleasure. Jenny Smith is a staff news writer for Science. You can find a link to the stories we discussed at science.org slash podcast. Stay tuned for our researcher, Benjamin Fernando. He talks about using seismic stations to pinpoint where space debris lands. Hi, Science Podcast listeners. This is Kevin McLean. I'm one of the producers on the show. I just wanted to hop in here before we get started to ask you to consider subscribing to News from Science. Every week on the podcast, we bring you one of the stories that the News from Science team has published, but there's so much more than what we can cover on our show here. For only about 50 cents a week, the money from subscriptions goes directly to supporting nonprofit science journalism, reporting on science policy, investigations, international news, and the latest breakthroughs from all around the world of science. Support nonprofit science journalism with your subscription at science.org slash news. You have to scroll down and click subscribe on the right side. That's science.org slash news. Earth's orbit is becoming more and more crowded with satellites and more and more are falling back to Earth. It's actually really not easy to track space debris during reentry, especially as it burns and breaks apart. This week in science, Benjamin Fernando and colleagues wrote about how to use seismic stations to track space debris. Hi, Ben. Welcome to the Science Podcast. Thanks for having me, Sarah. Sure. So why is it so hard to track stuff that's going at high speeds entering the atmosphere at some unknown angle? To understand it, let's talk a little bit first about how we track stuff in space. It sounds like it should be harder than it is, but you can either look at satellites in Earth orbit through powerful telescopes, or you can bounce radar waves off them. And either of those methods give us a really precise determination of an object's orbit. So we can figure out where it's going to overfly and when. The trouble is once you're below about 200 kilometers, 120 or so miles, something like that, the interactions between the spacecraft and the upper layers of the Earth's atmosphere become really chaotic. We can no longer predict with any particularly good accuracy exactly where a piece of re-entering space debris is going to enter the atmosphere. And if we can't figure out where it's going to enter, we can't figure out when it's going to enter. We don't have good radar coverage over the oceans or over a lot of the southern hemisphere. And so when these objects re-enter the atmosphere, very often we don't know exactly when or where that's going to happen. And even after the fact, it's not always clear where they would have either burnt up or fragments might have hit the ground. That is really surprising because you kind of feel like observed these days. And I was surprised to learn from your paper that over the horizon radar is classified. So even if you do have radar that's able to view something, you might not have access to it as a scientist or as someone tracking this kind of debris. Are there predictions about how common this kind of uncontrolled re-entry will become? Because this doesn't have to be the fate of everything in orbit that needs to be decommissioned, right? Absolutely. So there are ways of either moving satellites into higher orbits where they're stable for thousands of years or designing them in such a way that they break up high in the atmosphere, which folks are starting to think about, but certainly hasn't become an accepted norm as of yet. The big change that we've seen since 2020 is the rise of satellite mega constellations. So things like Starlink, where we're talking about companies not putting up a dozen spacecraft, but maybe a thousand or 10,000 over the course of a few years. In the first few months of last year, so in 2025, we got to the point where we were having four to five re-entries per day on some days. Those are obviously beginning to impact the composition of the atmosphere as well, because we're pumping it full of metals that you don't usually find at high altitude. The vast majority of those were Starlink satellites demising back to Earth. And if the rate of launches is anything to go by, the rate of re-entries is probably going to continue to increase at an exponential or near exponential rate over coming years. You use data from the re-entry of a Chinese craft, the Shenzhou 15, and this happened in 2024, to figure out if readings would give us this extra information and this tracking. Can you talk about the day that that happened when the Shenzhou re-entered and how easy it was to find out where it was going to end up? The object that we're talking about is indeed a capsule called Shenzhou 15. And what we're looking at is the service module of that. So it carried Tychonauts and Chinese astronauts into space and part of the spacecraft was left in a decaying orbit once they were done with it. And there were a couple of re-entry predictions that said re-entry will probably occur first few days of April, 2024. One of the predictions was somewhere in the South Pacific. The other one was somewhere in the North Atlantic. A really long way away, like nearly 20,000 kilometers apart. But as it happened, folks in California at about one o'clock on the morning of the 2nd of April were like, oh, OK, something weird is going on. There's really bright lights above metropolitan LA and people are understandably worried. You know, is it a missile? Is it a plane crashing? We figured out relatively quickly that actually it was a piece of reentering space debris that we knew was going to reenter at some point. Just no one had expected to reenter over California, pretty long way from the North Atlantic or the South Pacific. And they don't have any control over it, right? Like that's part of the problem here. Exactly. So most nations and companies do not do controlled demises on their spacecraft. It's now becoming more common, for example, the European Space Agency has done a lot of work leading on this to try and make sure that demises occur over the open South Pacific or even over Antarctica, where people are really out of harm's way. This particular object was just left in a decaying orbit It was inclined about 50 or so degrees which means that it overflies major population centers everywhere from London down to Melbourne on a regular basis Not great Exposing a lot of people to risk But actually it was kind of lucky that it was over California because there this extensive seismic network there. There are many, many stations. But reading this, I was immediately like, well, OK, why would a seismic station be able to detect something entering the upper atmosphere? So can you explain kind of why they're able to react to these entries? You're probably familiar with the concept of a sonic boom. And that's a shock wave, a nonlinear wave that's produced when an object travels faster than the speed of sound in a given medium, in this case, air. And objects that are reentering from space produce sonic booms. In this particular case, we have an uncontrolled reentry out of Earth orbit. But because the debris is still going really, really fast, so seven to eight kilometers per second, let's call it five miles per second, something like that. And you put it in mocks. What is it in a mock? So around Mach 25 to 30, so 25 to 30 times the speed of sound, that produces a really strong shock wave. And that shock wave is produced probably pretty high up in the atmosphere. We're thinking somewhere around 80 kilometers or so, we start to get really strong shocks. And those propagate down to the ground as sound waves. And those sound waves can be detected on seismometers exactly the same way that an earthquake happens. it will be detected on a seismometer. The only difference is that in this case, the waves are coming up, whereas from earthquakes, they tend to come from down. I really like this description. So it's like a cone of sound or shockwave around the debris and it's like kind of leaving these footprints as it processes across the land. I really could picture it. It's so interesting that you were able to capture this this way. I saw that the detection like this has been done for meteoroids before. So how is it different when you're tracking something that was human made? The difference is that space debris in particular tends to be made of many components that are of different strengths. You have solar panels, which are very weak. You have fuel tanks, which by their nature are very strong. The pattern of re-entry disintegration that we see is quite different. We're seeing some stuff break up very high in the atmosphere, but then we're seeing this kind of cascading failure mode where the bits that are broken off then break into smaller pieces, but some things survive a little bit longer and then breakup and so on and so on. So the key difference between meteoroids and natural space debris, other than of course the fact that meteoroids are coming from outside of orbit where space debris is not, is that breakup pattern is really different. And of course, the risks are very different as well. Meteoroids pose what we might call a kinetic risk. Things have been damaged by meteoroids striking the ground, those damaged houses, they've damaged cars before. Space debris can be a lot worse. So very often some of the components contained within satellites are toxic or flammable. There's a very famous example from 1978 when a nuclear reactor decayed out of orbit over northern Canada and spread radioactivity across this huge swath of the Northwest Territories. That's something that's really never relevant for meteoroids, natural meteoroids at least. What were you able to calculate about the debris and its path from the seismic readings that you used? The big thing for us was that we could recover the re-entry trajectory very, very well. It's a little bit to the south of what we might have expected from the prediction. Some of that probably due to the effects of wind. Some of that is probably because, as I said, the interactions with the atmosphere become really unpredictable. The other thing that we can do is we confirmed very nicely that the re-entry angle is actually really shallow. It's about one degree. That tells you something about how far forward, sort of along the surface of the Earth, those fragments are going to propagate as they are falling from orbit. Other than the trajectory stuff, so speed, descent angle, velocity, the other really interesting thing we were able to do here is constrain some of the breakup dynamics. And as I mentioned, if you're looking to recover fragments because you're worried about what they may contain, understanding how an object has broken up is really important. In this particular case, we detected what we call sort of coherent pulses, which look like they're associated with individual fragmentation events, that is, individual components breaking off the spacecraft and perhaps exploding or, you know, suddenly being exposed to this airflow at Mach 25 and failing. And from that, we can make some estimation of how the object broke up. And also we see clear evidence of what we call this cascading failure. So fragments breaking up into smaller fragments, which then break up. And that's really important from a debris perspective, because what we're interested in is, you know, did these fragments reach the ground? That's the kind of bottom line for us. The fact that you're using sonic booms, the objects are moving faster than sound. That means you're not really doing any predictions in the moment. This is no early warning system. This is, we now know where it went, and then you can go to that space and what, clean up, or you can't get ahead of this. Yes, absolutely. So the object, if it's supersonic, is always going to outrun its own sonic boom. You will see it go over and it will be gone. You might hear it a few seconds to minutes later. As you say, what we're really interested in here is taking very quantitative data from these seismometers, which is geotagged and has a very precise location to try and work out what that trajectory was and whether things might have fallen to the ground. California, as I said before, well-instrumented. Are there other places in the world where you could get this kind of data, or do we need to start deploying some kind of specialized stations to do this tracking? In some ways, I think we're very lucky that this first event happened in, I guess you could call it the spiritual home of seismology in Southern California. There are other places in the world with similarly good seismic coverage, so Japan, for example. But you're right, in most parts of the world, the coverage is more sparse. The other thing to think about, of course, and that we're starting to explore is there are regions of the world where space debris re-entries are of particular concern, either because of geology or ecology. We might think about instrumenting those areas more densely, for example. And the big advantage of these systems is you can get cheap seismometers that will cost you less than $1,000. The ones we're using here are a little bit more expensive, but they are a lot cheaper than building an entire radar system to track re-entries. Also, I mean, we don't want this to happen. If we're going to invest in something, maybe we should invest in figuring out how to decommission these without having them come down, right? Exactly, exactly. So the designing for demise, as it's called, is an active area of research. But I would say that the incentives for industry there are perhaps not where they should be at the moment because there is no pressing need to invest money in that because at the moment, everyone's just letting stuff fall where it falls. Thank you so much, Ben. Thank you for having me, Sarah. Benjamin Fernando is a seismologist and planetary scientist at Johns Hopkins University. You can find a link to the paper we discussed at science.org slash podcast. And that concludes this edition of the Science Podcast. If you have any comments or suggestions, write to us at sciencepodcast at aaas.org. To find us on podcasting apps, search for Science Magazine. or you can listen on our website, science.org slash podcast. This show was edited by me, Sarah Crespi, and Megan Cantwell. We have production help from Podigy. Our music is by Jeffrey Cook and Wen Khoi Wen. On behalf of Science and its publisher, AAAS, thanks for joining us.