Science Friday
Hosted by Flora Lichtman and Ira Flatow
A new simulation shows large amounts of hydrogen in our planet’s core. And, what scientists found in 290-million-year-old vomit.
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Hi, Ira here, and you're listening to Science Friday. Now for a deep dive to the center of the Earth to ponder what exactly makes up the Earth's core and how do they get there? A recent study tried to simulate conditions deep in the Earth using samples under extreme pressure and temperature. And in those simulations, they find that the Earth's core may have significant amounts of hydrogen locked away with iron and silicon. That finding has implications for how the planet formed and where the water on Earth may have come from. Joining me now to talk about studying the deep parts of the planet is planetary scientist Dr. Nat Shahar.
She's also Vice President for Research at the Carnegie Institute for Science in Washington. Welcome to Science Friday. Thank you so much.
For having me.
You're quite welcome. This is really one of my favorite topics because I've been studying this for years since I was a little kid with my golden book of the earth. Your group was not involved in this study, but has done similar work simulating conditions, right? Walk me through how this all works.
Yes, absolutely. So the way that it works is that we take two diamonds and we put a very small sample in between the two diamonds and then we squeeze the diamonds together, heat the sample with a laser that is shot through the diamonds and we can simulate the pressure and temperature conditions within the earth's interior.
So why do you need to do it this way?
There is no way to get a sample of the earth's core. It is very, very deep below our feet. So in order to understand what's happening down there, we have to be able to simulate the conditions of these high pressures and temperatures in the laboratory. And diamonds are the perfect way to do that because they are very strong and they are transparent to the lasers. And so you can heat things up to very high temperatures and you can also squeeze things to very high pressures.
Now, I know this research found large amounts of hydrogen, but we shouldn't be picturing it like a tank of gas or an ocean of liquid, right?
That's right. You should picture it like an iron alloy. So it's a it's a bunch of iron that in between the iron atoms and attached to the iron atoms, there are other elements like hydrogen or silicon or oxygen. It's kind of like how steel is not pure iron. It has it has carbon in it. It's an alloy of iron.
And do we know where all that hydrogen came from?
We would love to know. There are different ways of answering that question. So one of the ways that we think we could have gotten that hydrogen is from a hydrogen atmosphere that was surrounding the planet when it was very hot, very early on in its history and evolution. Another way is if the materials that the Earth formed from were very wet.
So if there is all this hydrogen, more than we thought before, does does that tell us anything about water? And where the water on Earth came from could have come from this hydrogen?
That's a really great question. What was shown in this paper and has been showed previously is that hydrogen really, really loves to be in iron metal. But that hydrogen needed to come from somewhere. And so what we think is that when the Earth formed, when planets form, if they were surrounded by a hydrogen-rich atmosphere, a lot of that hydrogen went into the metallic portion of the planet. But some of it must have also gone into the silicate portion of the planet, the mantle, if you will, of the Earth. And some of it will stay in the atmosphere. And so some of that hydrogen that went into the mantle and some of it that stayed in the atmosphere will end up becoming water on the surface of the planet.
And so indirectly, by seeing the hydrogen in the metal, we know there must be hydrogen and also water in other parts of the planet.
Do we have a sample? I mean, did we find samples from deep down with the hydrogen in the metals? Or is this just conjecture?
It's very hard to find hydrogen in iron metal because it diffuses very, very quickly. So we have looked. We can't find a sample of the Earth's core, but we do have iron meteorites, which are samples of planetary cores that fall to Earth. And we can measure those meteorites to look for hydrogen, to see if they agree with what we see in the lab. Unfortunately, hydrogen diffuses so fast that there's no way to see any hydrogen that could have been there in the iron portion of these meteorites.
Is there enough hydrogen in the iron in the Earth to have formed all the oceans and things on Earth?
Oh, yes, absolutely. There's tons and tons of hydrogen. If this paper is correct and other studies are correct, there would be so much hydrogen that we could easily have formed at least one or two oceans on the surface of the planet.
You know, I remember years ago when I was first researching this, scientists talked about something called the big burp. Which was during Earth's early years, all that volcanic activity when it was really hot spewed out all this hydrogen from below and that there was enough to form the oceans that way. And then then competing ones came later about comets and carrying all the water to the Earth. So which one is now in favor?
That's a very interesting question. I would say that studies like this argue that your first idea about the fact that the water or the hydrogen in the planet could come out and then form the oceans and also help with the atmosphere is very much in favor. The unfortunate part is that it's very hard to say that comets or asteroids did not bring more water to the planet. So the way that we would say it now is it's not necessary to have that second influx of water from asteroids and comets, that just planet formation in general could produce enough water to equal what we see on Earth today.
Does that change our thoughts on on which planets may have water, having to do with what's at their core?
Absolutely. So if forming water is a natural consequence of planet formation, because we see hydrogen in the cores of the planets and therefore they would be in the mantles as well, then it would imply that all the planets that go through this stage of a certain size that are rocky would also form water as a as a part of their planet formation process. So water would no longer be something that is hard to find on planets, but is actually quite ubiquitous on all planets.
What more do you want to know? Where are your interests lying in understanding the center of the Earth and our formation of the planet?
If I could do any experiments. On this topic, what I would want to do is to be able to directly measure and see where this hydrogen is within that metallic portion of the planet. And the reason is that in order to really understand what the Earth has gone through, we need to be able to say exactly how much hydrogen is in that metallic portion.
Mm hmm.
And while this paper has done a great job of getting us a little bit closer to knowing how much hydrogen is in there, it is still not 100% correct in the sense that hydrogen diffuses so fast that we are still not really able to get a direct measurement of the amount of hydrogen. So if I could make one measurement.
Yeah.
And I could tell you exactly how much hydrogen is in that metal and how much silicon and how much oxygen is in that metal at these conditions. I think that would open up an enormous amount of other information that will help us understand the formation of the Earth and the evolution of the planet.
Does that mean drilling a hole and bringing up an actual sample? I mean, there used to be a project Moho back in the 50s, right? About trying to do that?
Yes. If we could actually get a real sample of the core, that would be the most amazing thing ever. But every time we've tried, the pressures and temperatures just get so high that we're really not able to get even close. I think the closest people have gotten is on the order of tens of kilometers from the surface of the Earth. But there's still many, many, many more kilometers to go. But yes, if we were able to get an actual sample of the Earth's core, it would tell us a tremendous amount about the evolution of the planet.
All right, so we'll stay tuned, Dr. Shahar, for when that happens. You've been great. Thank you for taking time to be with us today.
Thank you so much for having me. I appreciate it.
Dr. Anat Shahar is a planetary scientist and vice president for research at the famous Carnegie Institute for Science in Washington, DC. Up next, Flora's got something you don't want to miss. That's after the break.
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Moving from the belly of the earth to another ancient belly, and what flew out of it? Scientists working in Bromach, or Germany, found, and I'm quoting, "the geologically oldest terrestrial regurgitulite, aka fossil vomit." It flew out of a nauseated ancient mammal ancestor, a dimetrodon, about 290 million years ago. And my next guest says it's an absolute treasure. Arno Rebeyar is a PhD candidate in paleontology at the Natural History Museum of Berlin and the lead author on a new study in Scientific Reports describing the discovery. Arno, is this like a bucket list item for you, finding fossilized vomit?
Yes, of course. It was not something obvious from the beginning, but it turned out super special. And I was definitely extremely happy to work on this extraordinary type of material.
What can you learn from it?
So actually, the precious thing about regurgitulites, we can learn a lot about which animal at which. And we can also say something about the coexistence of these animals. And I think that is probably the most precious thing about these fossils. Because in this small cluster of bones, we found three animals which were eaten by the same predator. So we can literally say that these three animals were living at the exact same time and at the exact same location, which is truly unique because we are here almost 300 million years old. So it is exceptional to be able to say that these animals were coexisting in, let's say, the same week,
maybe even the same day. And to be able to have this temporal resolution is really unique.
Because you know for a fact that they were living together, these animals, in a way that you couldn't know otherwise?
Yes, so we found them in the past already from the same locality. But you know, from layer to layer, they can be thousands of years or tens of thousands of years. So here, we really see the true coexistence of this taxa.
We've talked about coprolites, fossilized poop, on this show a lot. Aside from the obvious issue of which end the animal it came from, is there something else different about regurgitulites that makes them interesting?
So they are really similar in the way that they record the behavior of an animal, because it had some animals. So the information in the end is going to be a little bit similar, of course. But the way it is preserved, it has differences. For example, coprolites, because of the fact that the bones are more digested, and this will result in the matrix. So the sediment being around the bones to be very concentrated in phosphorus, for example. But in regurgitalites, we have a lesser digestion, and this will result in an almost absence of phosphorus. So these are some differences in the taphonomy, so in the creation of the fossils, which are really interesting and really new to us to investigate.
How should I picture this regurgitalite, this fossilized vomit?
So compared to, for example, coprolites. Coprolites are fossilized poo. And they are generally easily identifiable, because they have kind of a regular shape. For regurgitalites, they lack this kind of matrix around them, the matrix which was the fecal matter at the beginning. And so they basically look like bones laying on the surface of the sediment, like any other kind of fossils. But because of the way they are organized, but also the different animals present in there, then we can have a different explanation for the creation of such a cluster.
Oh, got it. Because it's not just bones from one animal, you're like, okay, this doesn't look like a regular fossil.
Exactly. This kind of cluster of bone has never been found before. And this locality has been excavated quite a lot in the recent years. So the fact that we found that there are three different animals in this small cluster really put us in the mindset of, all right, this is something special we have in the hand.
I mean, how rare is it?
Well, let's say it's pretty rare. And regurgitalites are quite new also in paleontology. So even if maybe in the past we found such weird cluster of bones, we did not necessarily think that this could be fossilized vomit. And now with the new techniques and also the new knowledge that we have from the recent years, now we can basically say this is the most likely hypothesis for the creation of this cluster.
Do you need extra special conditions to fossilize vomit? Because it's, you know... As a liquid base?
Indeed, and it is also very surprising to imagine a vomit to be fossilized, because we immediately have in mind something very watery or something very fluid that is just going to disappear in the first 10 minutes after it's deposited. But actually, first of all, we need to understand that even today, the predator are regurgitating quite regularly to expel what is difficult for them to digest, such as bone, feather, or fur. These are things that are harder for them to digest. And in order to save energy, they will then expel this content. And they actually expel a pellet that is quite cohesive, because all of the remains
will be surrounded by some kind of mucus and digestive liquid, which actually is going to make the whole thing really cohesive and really sticky. So when we have this picture in mind of something quite solid, we can actually imagine that it could get fossilized. So as for any fossil, the fossilization is an extremely rare phenomenon, and it needs to be buried very fast. So here, we can say it was buried in mud, and then the mud will solidify, and if we are lucky enough, there will be no destructive mechanism in the meantime, the mineralization we start, and then we will be able to have a fossil. But these are still extremely rare.
How does a paleontological world view excretions? Like, is this, are people like all dying to work on fossilized puke and fossilized poops? Or does it sort of rank lower than, you know, skeletons? What's the reputation within the field?
Well, that is a very good question. And actually, in the early days of paleontology, coprolites, especially because they were already recognized back then, were sort of curiosities. They were not really objects of study compared to skeletons or things like this. So there was this sort of vision of coprolites to be something not really serious. But as time As time moved on and now we have new technologies, more and more, we started to realize that coprolites are extremely important for us to investigate past ecosystems. And now, for example, we are able to scan in three dimension the coprolite and see everything that is inside.
We even were able to see that soft tissue can be preserved inside coprolite, which is extraordinary. We didn't know this before. And more and more, as the technology progressed, we realized that these are actually exceptional types of fossil and we need to study them. So I would say that today, this is more well-known, that these are actually really good topics for paleontologists to record past ecosystems, but also past behaviors. So there was really a big evolution compared to early paleontology and modern paleontology.
Arnaud Rebiyar is a PhD candidate in paleontology at the Natural History Museum of Berlin. Thanks for joining us today.
Thank you for having me. Thank you a lot.
This podcast was produced by Charles Berquist. Thank you for listening. I'm Flora Lichtman.
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