Asteroid Bennu contains building blocks of life
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Nature.

Welcome back to The Nature Podcast. This week, evidence of extraterrestrial brine from an ancient asteroid. And how a massive maze monoculture may have supported a South American culture. I'm Nick Pachachow. And I'm Benjamin Thompson. In 2023, a special delivery arrived in Utah, descending serenely beneath a parachute after travelling several million miles.

Inside the package was a metal canister containing samples of the asteroid Bennu, gathered when NASA's OSIRIS-REx spacecraft essentially fist-bumped the object, scooped up some of the resulting debris and ferried it safely back to Earth.

This week, two papers, one published in Nature and one in Nature Astronomy, provide more details about the rocks and dust that made up the sample, giving fresh insights into the makeup of Bennu and the four-and-a-half-billion-year-old parent asteroid it's believed to have broken off from. Together, they could tell researchers what the early solar system was like.

One of the teams behind this new research has found evidence of lots of different salts and minerals, suggesting the presence of an ancient brine. Now, when we think of brines, we often think of salty seawater, but brines can be much more complex than dissolved sodium chloride, and are of interest to scientists because they could be a place where the first tentative steps on the path to life began.

So,

So imagine you get some seawater and you evaporate it and you're left with little grains of salt in the bottom. The water evaporated from Bennu, but it leaves behind this mineral record. And as the water evaporates, the minerals come out in sequence. So maybe the most abundant thing in there comes out first and then the next most abundant and the one after that and the one after that and the one after that. And the way that the liquid evaporated to leave these different deposits behind is

is a key part of this puzzle, right? It can happen in different ways. There are a couple of different ways you could do it. If it were very cold and it were large enough, rather than lose the water by evaporation, you can essentially remove the water by freezing. As you freeze more and more of the

water into ice, you have less and less water. And as you do that, you end up with a whole lot of pure water ice and a little bit of water with these minerals in it. We think that Bennu was more like a wet mud, you know, that you had this wet mud and there were pockets of water under the ground. And as the mud dried out, cracks opened up and the water can evaporate through those cracks, ultimately reaching the surface.

And so, yeah, we don't see any evidence of the water itself. What we're seeing are the minerals that are left behind, the telltale signs of that water. So you've got these two different ways then, and you suggest that evaporation is the key factor.

But of course, Bennu now is an object, but it had to come from somewhere. Right. And I think in your paper, this result gives you an idea of what that something might have been like. Right. So Bennu is a rubble pile asteroid. So imagine there was an ancestral asteroid that broke up and some of those pieces combined to make Bennu. Some pieces may have combined to make other asteroids as well, but those little asteroids didn't.

didn't have the water on them. So Bennu never had this active brine that was precipitating minerals. That all happened at the birth of the solar system four and a half billion years ago on this ancestral asteroid. And we think that certainly had to be bigger than Bennu.

It had to be wetter than Bennu is today. Again, probably more like the consistency of a mud when that water was active. And it probably was colder. There are telltale signs in some of the elements that our organic colleagues are finding, things like ammonia, that suggest it may have been further out in the solar system than it is today. You know, we think of the asteroid belt

is between Mars and Jupiter. Bennu is actually a near-Earth asteroid. It's been knocked out of the orbit between Mars and Jupiter and come closer to the Earth. But the asteroid belt was really compressed from a wide range of solar system distances. Some may have been as

as far out as the gas giant planet today. And we may be looking at samples that came from that further out region of the solar system where it was colder and some of these brines could exist. And that word water obviously gets people excited when we're thinking about space. Sure. So if we have this asteroid then, and you're saying that there was some subsurface water that evaporated leaving behind these markers of a brine...

What is the evidence that you're putting forward that there was water there mean? And why is that interesting? It isn't just there was water. I mean, water is really exciting. We wonder like, where did the oceans of the earth come from? And water may well have been delivered from space, but this is a particular kind of water. This is a sodium rich water. We call it an alkaline brine. And these alkaline brines are special places because on earth they're rich in organic material. And,

And a whole host of studies have shown that these alkaline brines are one place that organic molecules can combine. We know that we didn't go straight from elements to, you know, some sort of thing swimming around in a brine. We had to form more complex organic molecules, which then ultimately combined to make something that could become life.

And we think these alkaline brines are the ideal environment for something like that to happen. And it's not just salt, as I understand it. There's a second paper out in Nature Astronomy, which you're one of the co-authors of, that looks at other interesting compounds, molecules, what have you. And some of these are essentially amino acids and pyruvate.

parts of the molecules that form DNA and RNA. How did this come about, do you think? So that's a really good question. It's hard to know at this point whether some of those were inherited into Bennu from the cloud of gas and dust the solar system formed from. Some of these could have formed before asteroids formed. Some of them could have formed in the asteroid. But the interesting thing is that we have them there. So we have five nucleobases

Think of those as the letters that in DNA make pairs and RNA are single. We have all five of these in the sample.

And so you're starting to look at a system where you have pieces of RNA and DNA. You have some of the amino acids, but you then have to combine those with things like, well, we find phosphate minerals, which tell us that there was phosphorus in the water. Now, if you've ever looked at a DNA structure, you know, everyone fixates on those pairs in the center, right? And they kind of ignore that big spiral thing on the outside edge.

But that big spiral thing is partially made of phosphate. And so now you're looking at having more than just one of the ingredients that go into these structures. And many of these minerals may have served as templates for organics. They allowed the elements to combine to make the organic molecules. And those are much more effective in alkaline and sodium-rich waters.

And so we not only have these ingredients, we now have the environment in which the first steps could have happened. And that's what's so exciting about finding these telltale minerals. I mean, you can imagine that people's minds could go into overdrive here and suddenly start thinking, you know, this is a strong indication of where life may have come from. But of course,

There are a dozen, hundreds of questions that need to be answered before you can draw a straight line between those two things. What are some of the key things that you want to address or that you think need to be addressed based upon this finding? I mean, I think there are

three things that you have to know, one of which would be direct evidence. Can we actually find, say, a nucleotide? But we also have to answer the question, how long did that water exist and what temperature was it? I like to make it like baking cookies, right? You can take the raw ingredients, you can mix them together in a dough, but if you just lay it on the countertop,

the countertop, it's never going to become a cookie, right? You have to have some time and some temperature to turn it into a cookie. And so that's one of the real questions that we can't answer from the organics. That's what the minerals are going to tell us. How long did these exist?

and at what temperature did they reach? And are those conducive to more complex reactions? Obviously, your work is evidence and you think this is what's happening. But there are folk who could say, well, you know what, actually, I think this happened in a different way. Could you conceive of these minerals coming about in a different way? Is it possible they were contamination, for example, or something like that? We spent a lot of time thinking about contamination. And all the evidence suggests that

probably isn't the case. These were very carefully stored. As soon as they hit the ground in Utah, within about an hour, they were inside of nitrogen. They've been carefully stored in nitrogen. And we know that, for example, we take them out of storage and put them in a scanning electron microscope. They spend 30 or 40 minutes in air in the process of doing that. And we haven't seen any changes in these minerals as a consequence of doing that.

So we think this process, while they can be altered, happens over a period of months. I think if people ask a question

did they really form this way if you think this was in the outer solar system why do you think these elements didn't concentrate by freezing the water rather than evaporating the water and things like ammonia would allow water to exist at temperatures of you know tens of degrees below the freezing temperature of pure water and so

Could we have had essentially a freezing happening rather than evaporation? And that'll come down to some really detailed work about things like the temperatures we talked about and the ability to measure the ages of these minerals, which we think we can do, but it's a very challenging measurement. So we've got these two papers then. Of course, this is a vanishingly small sample set that's been looked at.

What questions do you think other researchers might have? I think there are going to be several questions that come out of it, one of which is, why don't we see these things in meteorites? And one of the obvious answers is that a lot of these

minerals are not stable in the Earth's atmosphere. We saw this unfortunately, a few samples that were stored under good conditions, low relative humidity, but not in non-reactive nitrogen. We actually saw some of these minerals that were lost.

They're actually just disappeared because of reaction with the Earth's atmosphere. But we don't know if that happened in every meteorite. And so I think people are going to go back and say, are these evaporites more widespread? Because now that we know what we're looking for, maybe we go back and examine those. Or if a new meteorite is found that hasn't had so much reaction,

reaction with the Earth's atmosphere. Maybe we start storing that in a different way. I think people will look more carefully at the Ryugu samples, those brought back by the Japanese Hayabusa 2 mission. They have a few of these, but it's really, again, you have to go through a lot of samples and do a lot of work, and sometimes you just get lucky. But does the entire evaporite sequence exist on Ryugu or on its parent ancestral asteroid? And I think it's

It's also forward-looking because we are just sort of tasting what you might call a briny ocean that could exist in places like Enceladus or Europa. We obviously have a mission going to Europa. We have mission concepts to go to Enceladus. And in some respects, and I don't want to overstate this because a lot of people have been working on these issues for a long time through modeling, but from a sample perspective,

Is this our chance to see what those brines might really be like? Are we looking at a past ancient system that records the complete stage of where a modern system is today? Is the Enceladus subsurface ocean halfway through the process that ultimately produced the entire sequence of minerals in Bennu? And that's the questions that I think people are going to really be looking forward to.

Tim McCoy from the Smithsonian Institution's National Museum of Natural History in the US there. Look out for links to both the Nature and Nature Astronomy papers in the show notes. Coming up, the unexpected find that extensive maize farming may have supported the mysterious Casarabe culture. Right now though, it's time for the Research Highlights with Dan Fox.

Farming seaweed causes carbon to build up in the sediments underneath seaweed beds. And that could be useful to combat climate change.

Researchers analyzed a selection of seaweed farms worldwide ranging in age from 2 to 300 years old and with areas between 1 and 15,000 hectares. They found that older farms have more carbon in their sediments than younger farms, with the oldest site storing up to 140 tons of carbon per hectare. On average, carbon burial rates beneath seaweed farms were double those in nearby sediment unaffected by farming.

These findings suggest that seaweed farming can store carbon at rates comparable to the lower ranges seen in other marine and coastal ecosystems, like mangrove thickets. The authors say that farms hold promise for long-term carbon capture and storage. If that has captured your attention, you can weed out the details in Nature Climate Change.

In human society, urination is generally a private affair. But despite this, announcing your intention to visit the facilities will often inspire others in a group to head for the toilet as well.

This "contagious" urination isn't unique to humans, according to a new study of chimpanzees living in captivity. Researchers observed 20 apes at a sanctuary in Kyoto, Japan and found that urination events are more synchronised than would be predicted by chance.

In fact, the closer a chimp is to the first animal to pee, the more likely it is to follow suit. And individuals with lower status were more likely to follow the urination of others. The researchers say that their discovery highlights the social as well as physiological role of urination. If you're feeling the urge to read that research, it's published in Current Biology.

A system of giant earth mounds studs the savannah of Llanos de Moios in the Amazon basin in the west of South America. They are the remnants of a mysterious people known as the Casarabe. It's difficult for people to grasp the size of this construction, but like an average mound covers the area of 15, 20 football fields.

This is archaeologist Humberto Lombardo. And this is an average one. The largest one we know, this covers 20 hectares, which is 40 football fields in area. So these are millions of cubic metres of earth that have been moved to build these huge mounds, which have absolutely no practical purpose. Whatever the reason for the mounds, such large-scale engineering would have needed a lot of people, and you'd need to feed them all.

So how did they do it? We basically went there, we got some sample, we did some coring, etc. And then when we look, we say, wow, this is all amazed. Outside of the Americas, the cultivation of grains is thought to have allowed the older civilizations to reach higher levels of complexity, where they could have had organized labor to build great structures.

as the cultivation of grains allows a steady food supply so that more people can focus on tasks other than farming. One of the advantages of grains is that you can store them, and they are rich in carbohydrates, they have some proteins, so are quite nutritious. In the Americas...

In the Americas, the only grain crop available to the people was maize or corn. And there is evidence that people grew maize in Llanos de Mollos for nearly 7,000 years. But it's not been clear that it was the main part of their diet.

Societies in this region grew a lot of different kinds of food, and it's been argued that this mixture could have been the basis of the complex societies like the Casarabe, but that may not be the case. In a paper in Nature this week, Umberto and a team of researchers were interested to know more about the Casarabe, who lived in Claros de Moyos from around 500 to 1400 AD and who built the giant mounds.

Quite what these mounds were for is unclear, but they were also interconnected by canals and raised paths that were likely used for transportation. But Umberto was interested in something else, round depressions in the landscape. He was curious to find out whether these were also the product of the Casarabe or just natural formations.

But when examining them, he found something else. Now, it's not that I'm particularly interested in maize. This paper came out because we just found a lot of maize. It was quite an unexpected result. Umberto's work suggests that these depressions were made by people. But these people also seem to be growing a lot of maize.

but it's what he didn't find that confused him. The overwhelming absence of anything else, so there was only maize. By analysing the physical characteristics of the region, beyond just the depressions and through field surveys, Umberto determined that the Casarabe transformed the landscape to promote maize production. We found these two different types of landscape management. We have on one side drainage canals,

So they drain the water. So they basically remove the water from the landscape when the excess water is a problem. And then we have these ponds.

which retain water when the lack of water is the problem. Umberto suggests that the entire setup of depressions and canals appear to be designed to help the Casarabe people maximise maize production in both the dry and wet seasons. So we have the drainage canals that allow them to do agriculture during the flood, and then we have these ponds that retain water that allow them to do agriculture during the dry period.

So basically they double the harvest of maize and they can cultivate maize almost all year round instead of focusing on just one moment. Altogether, Umberto and the team believe that this evidence points towards the Casarabe having intensive maize farming, that they argue could have supported the society's complex culture. Now, among archaeologists and anthropologists, this word complex society is like

Very difficult to understand each other because each one of us has his own idea of what a complex society looks like. But I think that it is an expression of a society who has hierarchies, who has different people at different jobs. So there is like a stratification. And I will say that this kind of evidence that we get from the landscape are indicative of a complex society.

Tiago Germenegildo is an archaeologist who researches the Casarabe people and is not affiliated with the current study. He thinks that this new paper builds on existing evidence that maize was important to the Casarabe. It's very interesting that they managed to show that maize is cultivated

In this particular area, to such an extent, but this doesn't give us a general view of what they were consuming because they could be exploiting other areas and other parts that we still don't know. In fact, a few weeks ago, Thiago and a team of researchers published a paper in Nature Human Behaviour where they examined human remains of the cassarabe.

Their results suggest that maize was indeed an important part of their diet and that they even fed it to local ducks that they may have domesticated. But Tiago's work also suggested that maize formed a smaller part of their diet after around 1100 AD. When we look at other evidence from the same region, there is also an increase of palm remains in the same sites that I worked in. So it seems that over time,

It's not that maize got less important. My personal interpretation is that they expanded the network to other areas and had more access to more diversified types of diets. Thiago thinks that it's possible that the region Umberto and his colleagues looked at may have been one that was particularly good for growing maize, which would explain the intensive maize agriculture they found evidence for.

But other regions where the Casarabi lived may have been devoted to other crops, which would explain the more diverse diet Tiago and his colleagues found evidence for in the human remains. Tiago would be interested to investigate some of these other regions to see what plants the Casarabi were growing there.

Together, these papers show that there's still a lot we don't know about the Casarabe. For instance, we have no idea what happened to them. Their culture seemingly disappeared around 100 years before European colonizers arrived in South America. But understanding what food they grew could give us some insights into how they lived and how their culture developed. But even that raises questions.

Maize was grown in this region for a long time. But evidence suggests that people there didn't always rely so heavily on it. So Umberto wonders what changed for the Casarabe to devote so much of their energy to it. And the question is why, after 9,000 years, out of the blue, they decided to switch to agriculture? I mean, why didn't it happen 2,000 years earlier or 5,000 years earlier? They had everything. They had the plants, they had the seeds.

So there is something that happened like 1,000 years ago that made these people completely change the way they lived there. That was Humberto Lombardo from the Autonomous University of Barcelona in Spain. You also heard from Tiago Hermengildo from the Max Planck Institute of Geoanthropology in Germany and the University of Sao Paulo in Brazil. For more on that story, check out the links in the show notes.

Finally on the show, we've got an AI story. As the release of a model from China called DeepSeek R1 has spooked stock markets, dented supposed US superiority and thrilled researchers.

Nature's European Bureau Chief, Nisha Gaines, has been following this story and she joins me now. Nisha, hi. Hi, Nick. Well, thank you so much for joining me. So, first of all, DeepSeek has been in the news a lot recently. Can you give me a roundup of what exactly it is and maybe how it differs from other AI models people might have heard of? Yes, this is all anybody is talking about this week. The reason that it is such big news and is exciting so many people is

is that it seems to be a very advanced reasoning model. These are these large language models that can generate responses by this step-by-step approach that seems to approximate human reasoning. And it's competing with the best models that are out there, notably OpenAI's O1 model,

But the thing that is really exciting people is the fact that this model is open. It's been released with open weights, which at the moment is still pretty unusual in AI. We've talked before on the podcast about various different kinds of openness in AI models, and it's not always what people expect.

So what does open mean in this particular context? Yeah, so there are some subtleties here. DeepSeek R1 has been released with open weights, and that means that the parameters of its training have been made public. But importantly, there is a distinction with deepseek.

a model that would be considered fully open source and R1 isn't considered fully open source because its training data haven't been made available. But importantly, the code is available and that means that researchers around the world can study it and they can build on it.

And speaking of researchers, in the headline for Nature's Story on this model, we say that it thrills scientists. What is it about it that has been so exciting for researchers? So the really exciting part is that openness, the fact that they can look at the algorithm. In many cases, they're able to run it from home if people need.

have enough computing power. There's lots of researchers who are able to run DeepSeq locally, but it gives researchers the opportunity to actually look at essentially how these models think and

and gives them more insight into that because the other well-known models that have come from OpenAI and other US tech firms typically, they are pretty much black boxes. They can't be interrogated by researchers. And that means that it's more difficult to figure out how these incredibly advanced technologies

Models are doing these extraordinary things like writing code and doing chemistry problems and quantum problems. And that's the meat that scientists really want to get at. And DeepSeek seems to provide the best opportunity for them yet. And the other thing that people seem to have been quite excited about is the cost of this model. So as I understand it, it was quite cheap to make.

and also is quite cheap for people to use as well. That's right, yeah. So the cost is one of the things that has really sent shockwaves around the world, and it was a bruising day for US tech stocks this week because of the perceived threat that this cheaply built and cheap-to-run model poses to the more expensive US-built models.

The training of AI models in part is to do with the types of computer chips that are needed. And often there are thousands or tens of thousands of computer chips called GPUs are needed to train these AI models. And that can cost tens of millions of dollars we've seen in the US. And that poses all sorts of questions about energy consumption, which is expensive, and

And the reported figure for deep seeks training is only about $6 million, which is extraordinary when you compare it to something like Lama, which is from Meta, which costs upwards of $60 million reportedly to train. But as I understand it, they haven't released the full cost of the training. So that may be an underestimate, right? Yeah, there are some questions about what the actual cost is.

We don't have an exact read on the costs and there are some questions about what chips and what computer hardware they have actually done it on. In terms of them doing it with low cost, there's also been some discussion about how they may have managed it with less resources as well, because there's been export controls on the type of GPUs that Chinese firms can use.

Can you tell me a little bit about this? How have they managed to create this model despite these constraints? Yes, that's right. So the main restriction there is that the US had put export controls on these computer chips called GPUs, graphic processing units, the most advanced kinds to intentionally stop innovation in China and to create more competition between the US and China.

So there are reports that DeepSeq already had some NVIDIA chips, NVIDIA, the big US tech company that has built its value on being the main maker of these chips. But the lack or the restricted amount of chips and computing resources seems to have driven DeepSeq to innovate, innovate in lots of ways, including algorithmically. So to build chips,

a type of model that is able to train on much less computing power than the other models that we know of. And can you tell me a little bit of how they were able to innovate in this way? What was it that they were doing that's maybe different from what other models were doing when they were being built?

So there will be a lot of things that will have contributed to that. But one of the key ones seems to be what happened in the process called reinforcement learning. And that's a really crucial part of training these models. And that's where the model is rewarded for reaching a correct answer and for working through problems in a way that outlines its thinking.

And with DeepSeq, the team was able to estimate the model's progress at each stage rather than evaluating it using a separate network. And that helps to reduce the training and the running costs. And so as we talked about, this new model release has sent shockwaves around the world. What do you think it means for the future of AI? The news has come at a really interesting time in global politics today.

and global competition in AI. DeepSeek R1 was announced on the same day that President Trump was inaugurated in the US, and shortly after that, he announced a large AI program in the US to increase competition there. But US tech companies, AI companies have clearly been threatened and have sat up and taken notice of what DeepSeek R1 has been able to achieve on a relative shoestring level.

So we are already seeing big companies there responding to that. OpenAI has said that it will accelerate the release of some of its next reasoning models. Those tend to be thought of as the leader models.

And even in the days since DeepSeek R1 was announced, DeepSeek, the firm, has already announced another AI model called Yanis. And there are also models coming out of China, including from one of their big firms, Alibaba. So I think we will see...

a real intensification in the AI arms race, especially between China and the US. And there'll be a concentration on things like running costs, what these models are being trained on, and importantly, how researchers can continue to innovate algorithmically to bring down some of those costs, which have caused so many concerns

in terms of energy and so on. Well, it seems that it's all to play for in the world of AI and nature will be keeping an eye on that story. But for now, Nisha, thank you so much for joining me. Thank you. And listeners, for more on that story, check out some links in the show notes. And that's all for this week. As always, you can keep in touch with us on email. We're podcast at nature.com.

You'll also find us on Blue Sky and X. I'm Benjamin Thompson. And I'm Nick Pachaciao. Thanks for listening. At Verizon, anyone can trade in their old phone for a new one on us with Unlimited Ultimate, which means everyone in your family could get a new phone and stay on your family plan, keeping you close. Hey, Mom, you seen my toothbrush? Oh, maybe too close.

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