Why we can't announce life on Mars (yet); The Romans' impact on the British economy; Link between exercise and your microbiome

0:00This episode is brought to you by Accenture. When your advertising operations fall out of sync, Everything else follows. Spotify and Accenture are working together to reinvent the rhythm of ad sales, using automation, analytics and smarter workflows to simplify campaign delivery and access better data across the business. The result? Less time spent on operations, more time connecting brands with the moments and fandoms that matter most. Learn more at Accenture.com slash Spotify. We're talking about what is starting to look like a compelling case for life on Mars. This was the Perseverance rover driving over an ancient lake bed on Mars, investigating some rocks in an area they're calling Bright Angel.

0:42This is a potential biosignature. It's not life evidence, it's not a biosignature, but it poses to us a question of, we need to look at this in more detail. And we haven't had something like this before on a mission. We have to really seriously consider the possibility that these features were formed by living things on Mars more than three billion years ago. It really does seem like life had to be involved. Life on another planet. What have the Romans ever done for us? Is there anything we can still blame the Romans for? Well, I mean, as we're about to learn, some heavy metal pollution. If I asked you to tell me what you can do to improve your microbiome.

1:1830 plants a week. Fermented food, of course. Fibre. Exactly, yeah, but you missed weight training. I did. Are you going to start thinking about it? I'll start thinking about it. How about that? Hello and welcome back to the world, the universe and us, the weekly news podcast from New Scientist. I'm Dr Penny Sarche. And I'm Dr Rowan Hooper. On today's show, we're going to hear new evidence about what the Romans did to the British economy after they left. And we're going to learn about how exercise can influence your microbiome in unusual ways. But we start with the small matter of, well, the microscopic matter of life on Mars.

1:55Life on Mars. NASA have just held a press conference on this. It's not life on Mars currently, but it's the best evidence we have for past life on Mars. It is very exciting. It is. I mean, this is the story I've been dreaming of all my life, not even all my career. Really? Well, you know, life on another planet to actually find it. I've been such a sceptic until just recently the evidence is just really starting to line up. Well, we're not there yet. Yeah, sorry, fine. To put it more conservatively, this is analysis of mudstones on Mars that's found features that are consistent with biological activity.

2:30So this sounds familiar. We did this in March, didn't we? We did. We're super ahead of the curve. This was work presented at the Lunar and Planetary Science Conference in Texas in March. And now that's been published in Nature. OK, so now there's a big unfair from NASA and the like about it. There is. And look, it's such interesting work. It's worth returning to to dig into it some more. Yeah. So let's set the scene here then. This was the Perseverance rover driving over an ancient lake bed on Mars, investigating some rocks in an area they're calling Bright Angel. Yes. Nice name. It is. Well, it's lightly coloured.

3:06And when they saw it in the distance, they just named it Bright Angel. Sure. And these rocks are particularly exciting that they found there because there's these speckles on them. Some are called leopard spots, if you remember. Others are called poppy seeds, they've called. and these are similar to patterns associated with microbes on Earth when they're performing redox reactions. Yes, so redox reactions, that's oxidation reduction reactions when molecules either lose or gain electrons, if you remember your school chemistry. Yeah, well, I did have to look it up. I always get it one way around.

3:36Leo the lion says, gah. Oh. Loss of electrons is oxidation. I was going to say oil rig. Oh, yes, that's the other one. Oxidation is loss. Yeah. Reduction is gain. And so the work is all about these redox reactions. On the Martian rock, they've got these little green flecks of materials that show this redox. But the exciting new thing is that the distribution of these speckles is uneven and it's really related to the concentration of organic compounds. So that does add weight to the idea that there were living organisms that have actually generated them. And let's talk then about this, why redox reactions are so exciting.

4:16What have they got to do? Yeah, so I wanted to get into this, and I asked Mike Tice about that. He's an astrobiologist. He's an author of the Nature paper. He's at Texas A &M University, and here he is. Anyone who's ever used a battery to do something is already familiar with the idea that you can use the movement of electrons from one place or another to do useful work. That's all redox reactions really are. It's the movement of electrons from one place to another. And when that movement of electrons releases energy, that can potentially be harnessed to do something else. Well, batteries are a relatively recent thing, but organisms have been doing this on Earth for billions of years now.

4:57One of the redox reactions that we infer was important in making these things was the generation of sulfide locally from things found in the rocks, sulfate, salts, and organic matter. Now, there are abiotic redox reactions that will do exactly that. They'll generate sulfide from sulfate and organic matter. But we've been studying those things for various reasons for years now, and all of them appear to run very slowly at the sort of normal surface temperatures that we think these features formed at. And I mean slowly, even over geologic time periods. So in order to get any meaningful sulfide generated, we think abiotic processes likely would have required temperatures above around 100 to 120 degrees Celsius.

5:44As far as we can tell from the instruments aboard Perseverance, these features formed at lower temperatures, like the kinds you'd find in normal mud around a river or a lake. So abiological processes would have had a hard time making these particular features. On the other hand, we know that organisms on Earth have been doing exactly that process for more than 3 billion years. And so we have to really seriously consider the possibility that these features were formed by living things on Mars more than 3 billion years ago, living in ancient mud around a river or a lake. So to sum up all of that, this is evidence for a chemical process that can be explained without life being present.

6:28But it is hard to see how it would work at the warm temperatures in the sediments that we know were on Mars billions of years ago. Yeah. Given the ways that we know that these things can occur, it really does seem like life had to be involved. Yes. Yes. Seems like that. Yeah. Yeah. So I also spoke with Sanjeev Gupta. He's an extraterrestrial geologist. Great job, Ty. Isn't that a great title? Yeah. Add that to the list of things. He's other things as well, but I just want to read only that one out. Imperial College London. And he's been working on analysing these results as well. And here he is.

7:02Sanjeev, thanks for joining us. Let's start with the title of the paper, Redox Driven Mineral and Organic Associations in Jezero Crater Mars. Now, it's quite understated, isn't it? It's quite downplayed. Yeah, because it is about these very complex chemical reactions that occurred on Mars billions of years ago. So it's, you know, it's not like we haven't found a fossil. So the paper is really about this very detailed chemistry and the geological interpretation that surrounds it that has these interesting possibilities. Well, that's still being very understated. I'm very excited. I mean, how exciting is this for you in terms of your career?

7:50I think for me to be part of this is extremely exciting. I'm not going to be the person who analyzes this sample whenever it comes back. But I think it's the first time we have something that has the potential to be once examined on Earth in Earth laboratories, has the potential to have some major implications. Okay, Sanjeev, tell us about the context in which these minerals have been found, and perhaps a little bit about the chemistry involved. Yeah, so we drove into this valley, this river valley that cuts through the crater rim of Jezero and feeds the delta that we see on the western side of the crater.

8:30And we saw these really light toned rocks that were named the Bright Angel Formation. What I've done specifically is to really kind of map out and look at the details of the geology of these rocks. And they turn out to be, the rocks when we examined them, turn out to be very fine grained. They're laminated. And our interpretation is they're actually the deposits of ancient lakes, basically. So this valley was basically filled with water and we had deposition of fine grained sediments. from that water column supplied by rivers likely into this water body. So we've got a habitable environment. Then when we looked in detail at some of these mudstones, firstly, we saw in one place we found these really peculiar spots, what we've called leopard spots.

9:20So the mudstone itself has got this reddish colour. It's sort of rust, basically. It's very iron. And then within that, we see dispersed throughout that in a kind of random pattern, if you like, are these spots with dark rims and light-toned cores. And the light-toned cores is where the iron, the ferric iron, has been reduced to ferrous iron. But we also see in the cores, the rims, we see sulfides and phosphates, basically. And this is what's the interesting thing, isn't it? Because on Earth, those kinds of redox reactions are associated with life, mostly. Is that right? Yes. And most people believe that on Earth when we see these and that they're not uncommon in Earth rocks, going back to what we call reduction spots, they're typically associated with microbial activity.

10:17So the other big part of the puzzle is that also throughout the sediment that we see here, the mudstone, we have the Sherlock instrument, the Raman spectrometer, which looks for organics, has discovered organics distributed throughout. Organics don't mean life, but carbon compounds, but they're distributed throughout. So they've probably been involved in these redox reactions. And what happens on Earth typically, but there are abiotic mechanisms also, is that microbes will use these organics for energy, basically, and drive these redox reactions, basically. And so the idea, the paper is, and the data suggests that these special minerals, these redox minerals have been formed because of these redox reactions.

11:03Now, what we do in the paper is present two different scenarios, one an abiotic scenario, which you can create this just without biology. And then another possibility is one that involves biological processes. And both options are open. So what we do is we say basically that this is what we call a potential biosignature. That means it's not life evidence, it's not a biosignature, but it's something that poses to us a question of, we need to look at this in more detail to see if this is evidence for biological processes and this is a sample that we need to return. And we haven't had something like this before on the mission.

11:49So this is the first time something that says, oh, this could be formed due to biological processes. And that's why the excitement is there. I mean, what it does seem we can say is that we've got these redox reactions going on on Mars. We know that. We know that they are the basis or a basis for the emergence of life on Earth. So we can't say what's happened on Mars in any detail yet. But we can say perhaps that the chemistry needed for sort of proto-life certainly has been operating on Mars. That's right. And we have the conditions. And I think that's the key, is that the context tells us. These are not out of context, the fact that we have.

12:32And that's, in some ways, that's really what gave us confidence in this paper and the results, is that, you know, firstly, we have this environment, that habitable environment. We have this detection of organics, the G-band signature in the Sherlock-Brahman spectra. And then these peculiar leopard spots suggesting redox reactions. So we really have to get this rock back to Earth. We do. And that's a hot topic at the moment. I did hear that that's the reason why NASA have made this big press briefing about it. I mean, obviously, it is a big deal. It's a big, interesting result. But they want to make it, get it into the news because they need to secure funding for sample return.

13:18Right. So there is a political angle here. We know that the Trump administration really wants to slash NASA's budget and that would sort of kill our chances of getting this sample returned to Earth. Yeah, exactly. So this is about putting pressure on. And you've got to hope that the possibility of finding life appeals to this administration. But as Sanjeev said there, we can still build the case even while still on Mars if we find more evidence of the same redox reactions elsewhere. elsewhere. So it's just basically replicating what they found like any good scientist would want to do. But I just want to step back for a minute because we're talking about what is starting to look like a compelling case for life on Mars.

14:02Yeah, it's extraordinary, isn't it? Like I say, I've always been not that interested because I didn't think we were going to fight, but this is actually quite convincing. It is hard not to get carried away, isn't it? And I I tried to draw out the scientists on this that I've spoken to because the immediate thing I thought of is supposing life arose on Mars. If it did, it's around the same time that it arose on Earth. And then you could think, well, did one seed the other through meteorites, you know, being knocked off the planet onto the next planet? I've been thinking about it a slightly different way.

14:35Like after the birth of our solar system, it's only a matter of time before life arises wherever it can. but it managed to continue living here and it couldn't own Mars maybe? Well, so that is the other mind-blowing alternative. Yeah, both are mind-blowing. Yeah, that life is easy to get going. It started on Mars and Earth independently. So which is more mind-blowing? We're Martians. Either we're Martians or we sent life over there. Or life is just common throughout the solar system. I'll take any of those options. All very exciting. So luckily the scientists are not getting as carried away as we are.

15:16That's our job. Not surprised. Their job is to actually find the data first. But we wait, see more. This episode is brought to you by Google Chrome. You think you know a browser, but Gemini and Chrome, that's new. It can help you with practically anything on the web, like restoring a vintage motorcycle from a 50-page restoration block or finally break down that long article you've had open for weeks. Gemini and Chrome is here for it. Ready to make anything online make sense? There's no place like Chrome. Check responses set up required. Compatibility and availability varies 18+.

15:51It's time now to talk about the Roman Empire in Britain. And we are legally obliged, I'm told, to start the piece by asking, what have the Romans ever done for us? And in this instance, let's put ourselves in the position of the British people in the early 400s as the Roman Empire was faltering and collapsing and the Romans withdrew from Britain. Yeah, because the argument has always been that when the Roman Empire withdrew from Britain, it left behind chaos and economic collapse. But that's not the case. It's just what the Romans wanted us to think. Well, yeah, maybe. That's the narrative. But that's not what apparently we're learning now.

16:31And Mike Marshall, science writer Mike Marshall, is here to tell us the latest. Mike, is there anything we can still blame the Romans for? Well, I mean, as we're about to learn, some heavy metal pollution. We can definitely blame them for that. All right. So give us some details, Mike. Yeah, sure. So as you were saying, the narrative that historians have been telling for many years is that as the Romans withdrew from Britain, that basically created chaos. You know, there's no sort of state power. There's no one around to sort of organize everything. And so the result is economic collapse. And there has been some evidence from that from certain kinds of industry.

17:07but it's not what we're seeing from this new set of archaeological results, which seems to suggest that, on the contrary, metal production, metal processing, went on basically uninterrupted and, if anything, increased. So heavy metal is worthwhile after all? In many respects, Rowan. This comes from an archaeological site at Albra in North Yorkshire, in the northeast of England. And this was, during Roman times, this was a major town. It was called, and I'm going to mispronounce this probably very badly, Isurium brigantum. And it was a major sort of like mining area and metals processing area. And the archaeologists have discovered, among many other things there, a silted up riverbed.

17:53And this riverbed contains layers of sediment in which are trapped aerosol pollutants from the metal processing. So by digging down through those layers and measuring the level of metal pollution, they can actually track how much or how little metal processing was going on. Wow. So we were polluting our rivers even back then? We were pretty, yeah. Oh, yeah. And so they have this incredibly long chronology that goes from 345 AD to 1779 AD. So from the late Roman period, right the way through almost into modern times. and very nicely they can in the more recent periods where we do have really good historical records it all nicely lines up you can there are periods when it's recorded that you know metal processing declined for whatever reason and you can see that reflected in this record so that gives us a lot of confidence that what they're finding for the late roman period is correct it's amazing to think of mining happening for such a long period of time so many different sort of stages and there must have been some really big ups and downs in the industry through that kind of big data set?

19:02What are we talking, 1500 years nearly? Yes, yes. There's a lot of sort of very dramatic ups and downs, but some of them not quite when you would expect them to be. So as you mentioned, in the late 300s, early 400s, that's when the Romans were sort of gradually withdrawing from Britain. People pinpoint sometimes the year 410 as like the Roman withdrawal. That's a bit arbitrary. It was a process, but around then. And so, you know, there's the Roman government apparatus goes, the tax collection system goes, there's no new coinage being brought in. And as far as we can tell, all, almost all of the field armies leave as well.

19:42and yet what we see in this metal in this metal pollution record is that a very very slight decline but really you know really not very much at all and then it actually gradually levels gradually then increase over over the subsequent decades and the subsequent century so you know what you're looking at is sort of continuity um and then actually a ramping up of production So you see, there were these environmental regulations in place when the Romans were here. They left and we just then ignored them all, went our own way and had to reboot the economy. It sounds like something that happened. It's like you're reaching for an analogy here.

20:23Yeah, really reaching for an analogy there. That doesn't work. No. Okay. So we don't know exactly what was sort of behind all this because there is a lack of written records from this period. But one of the things that we do see is that in the first half of the 500s, there is a fairly dramatic increase in metal processing. And one of the researchers I spoke to, Jane Kershaw at the University of Oxford, who wasn't involved in the study, but does study this sort of period, she suggested that this might be to do with increased fighting at the time. So basically there were all these sort of different Anglo-Saxon and whatnot kingdoms sort of jostling for place in the British Isles.

21:05And there was a very strong like martial culture. Like it became very sort of important. There's lots of graves from this time where people are buried with like swords and knives. And that kind of thing is clearly sort of valorized and important. So she suggested, you know, we can't be sure about this, but she suggested that maybe it's to do with all this sort of internecine fighting that was going on. I'm not sure a post-Empire boom in the weapons industry is such a great thing. Well, no. In fairness, the Romans did a fair bit of fighting themselves too. True, true. So, you know, it was a good time to be in the weapons business.

21:42Were there any other parts of industry that kind of did better than we thought once the Romans left? Yes, there's several things that did sort of survive. So one of the one of the authors, Christopher Loveluck mentioned to me a site called Droitwich in West England, where there's basically an unbroken record of salt production, right from from Roman times right through basically to the present day. Partly because I think just salt is just such an essential of life, you know, you need it for like food, food preservation and all kinds of other things. So people stuck with that. Oh, because the word salary comes from salt.

22:17Romans really valued salt. Very good Latin knowledge. Mike, so I've heard vaguely some talk that this label that we call this period, the Dark Ages, people don't like that anymore. But I can't. I mean, is that is this sort of supporting that rejection of the label of the Dark Ages? Yeah, it very much is. It very much is. So the label of the Dark Ages is it's hard not to be too blunt about this. is to some extent a sort of a late an idea that was imposed later mostly but largely by like powerful christian and christian groups and like monarchical groups who were trying to sort of draw a contrast between you know the state of the you know medieval christian power structures in europe and this previous chaotic period that they wanted to distinguish themselves from the basis for it is that you know there's relatively few written records from this period And some industries did apparently fall off a cliff.

23:13So there's a big decline in wheel-thrown pottery, for example, after the Romans leave. They love pottery. We do love pottery. But on the other hand, other things seem to have thrived. There's a spectacular metalwork, and I don't just mean swords. There's all these amazing sort of elaborate brooches and things that people were wearing. if you look at the stuff that was recovered from the Sutton Who gravesite some of this stuff is absolutely spectacular incredibly intricate and that's all from the supposed dark ages I'm glad what should we call it now? I've heard scholars call it late antiquity and that immediately makes it sound more interesting and glamorous because the Christians who came after the dark ages did some pretty dark things themselves right it's a bit much of them to say it was the dark ages before them One for another podcast, I reckon.

24:07Maybe on another channel. Thanks, Mike. My pleasure. Now, Rowan, I reckon if I asked you to tell me what you can do to improve your microbiome, you'd give me loads of good tips. Maybe not loads. I'd give you some. So, you know, there's this 30 plants a week thing that I try to vaguely follow. Yeah, same. At least, you know, diversify as many plants as possible. and then fermented food of course miso kimchi as much as that's possible fiber yeah and the idea with with both of those is to or all of those things is to increase the niches available in your in the food in your gut for bacteria to colonize and so diversify your microbiome exactly yeah but you missed weight training i did weight training yeah so this is a new finding that people who respond well to a weight training program also see an increase in the desirable gut bugs that they have inside them, including bacteria that produce chemicals that can help protect the gut and reduce inflammation, all the good stuff.

25:09Brilliant. But how is that connected? Yeah, exactly. So apparently we already knew that aerobic exercise running and the like does seem to help good microbes grow in our bodies, although it's not fully clear why. There are a few theories. One might be changes in our hormones or our blood circulation have an effect in some way or maybe exercise produces things like lactate that for some reason shape our microbiome but anyway we don't really know why and we also didn't know if these benefits come from other types of exercise like resistance and weight training. So to find out a team involving Sven Nansen at the University of Tübingen in Germany recruited 150 sedentary adults it's probably quite easy to find most of us are more sedentary than we should be and they gave them an eight-week training program that included exercises like things like chest presses, seated rows, other resistance exercises.

25:58I mean that makes me feel tired and I'm not that sedentary. How do we know they kept up this regime? Yeah always tricky with studies like this but this is one of the cool bits in the experiment. As David Robson reported for us they used smart strength machines and what these can do is they monitor your progress and they adjust the weights and the range of motion accordingly so it's sort of personalized but at the same time It logs exactly what you're doing and sends all of that data to the scientists so they know if you really did it or not. Very fancy. Very fancy. And then they had to make them do a poo sample.

26:30Yeah, exactly. If we really want to get to the microbiome, there's always poo involved. Everyone had to provide a stool sample at the start, middle and end of this training program. Okay, so only three. That's not too bad. And so they found, after all this, that weight training, even if it's not dramatic, is somehow good for the microbiome. Well, sort of. It's actually more intriguing than that. They found that the people who responded best to this training program, so their muscles gained the most power, those were the people who also had this beneficial increase in the good gut bacteria. Is there a correlation causation thing going on here?

27:09Yeah, so what's causing what, right? So it's possible that those who are really like vibing with the program and getting on with it, maybe they started eating more healthily and then that could change their gut bugs. But equally, maybe those that sort of started off with a better starting culture of gut bugs, they might have contributed chemicals that somehow helped with muscle growth. There could be even a sort of two-way street going on. This just kind of adds to a lot of new stuff we're hearing about weight training, the benefits of it. Yeah. Which I've always, like, sort of not turned my nose up, but just not really been interested in it.

27:45It's not really for me. Yeah. As you can tell. Well, I don't like to say, Rune, but there is a growing body of evidence that there's all kinds of benefits. And Grace Wade has written about this for us in the past. It's surprising how rapid some of the changes can be if you do start doing weight training. Apparently, a single session of strength training boosts the activity of genes and the muscles involved in dampening inflammation and that kind of thing. And this is really motivating. if you're a beginner you're likely to feel stronger in only around three weeks because your nerves and muscles get better at communicating quite quickly and you really sort of feel that impact motivating it is isn't it well yeah i think so anyway are you are you going to start thinking about it think of your microbiome i'll start thinking about it how about that but i i know you're big on kimchi and stuff but what i will just point out is um another thing i learned from grace is that the evidence for the health benefits of fermented foods is actually not quite as there as some people might suggest.