Dr. Oliver Warr collection groundwater sample by Dr. Oliver Warr - University of Toronto

Cracking the Secrets of Billion Year Old Underground Water by Dr. Oliver Warr

Dr. Oliver Warr - 3 km underground in a mine, Dr. Oliver Warr, research associate in the Department of Earth Sciences at the University of Toronto, Canada
Dr. Oliver Warr - 3 km underground in a mine, Courtesy: Stable Isotope Lab

Cracking the Secrets of Billion Year Old Underground Water by Dr. Oliver Warr

We (ON) are thrilled to be able to have an enlightening conservation with Dr. Oliver Warr (OW) on his team’s discovery of 1.2-billion-year-old groundwater deep in a gold- and uranium-producing mine in Moab Khotsong, South Africa. Dr. Warr is a research associate in the Department of Earth Sciences at the University of Toronto and the lead author of the study. As to the significance of this discovery, Dr. Warr stated that it sheds more light on how life is sustained below the Earth’s surface and how it may thrive on other planets. Their findings were published last week (July 2022) in the prestigious journal Nature Communications. This is the press release.

Below, please enjoy our in-person conversation with Dr. Warr.

ON: Thank you so much, Dr. Warr, for spending time with us during your busy conference schedule in Hawaii. First of all, we want to know if you could explain your research to us in layman’s terms.

OW: Yeah. That’s perfectly fine. I think the best place to start, actually, is almost 10 years ago when there was initially a study on the Canadian Shield which identified that in the deep crust you can have water trapped underground for up to a billion years. At the time this discovery was a ground-breaking study. It was amazing because it revealed that water can really be trapped underground for long periods of time, much longer than we thought.

But the question there was, well, how common is that? Where else in the world might it be? Is this just one single point where everything is aligned to make it that old or is it a much broader phenomena that we are only just seeing one particular case that we’ve only been able to solve once.

From that point the hunt was on – let’s understand this water because to put it into a bit more context, these rocks represent 72% of the surface area of the crust. These environments are very global so they can contain up to 30% of all groundwater.

But how old is it? Where did it come from? What does this mean? What processes are generating and ongoing in this region? That’s what we didn’t know. And that leads us to this current work. We went to a completely different part of the world, a place in South Africa, and we went down a deep and dark mine, and we again found that ancient water. It is as old as we found in Canada. So in a completely different part of the world, we found that water had been trapped underground for 1.2 billion years. And this was incredible because what it really means is that this is a feature of these systems in general, that water can be trapped on billion-year time scales in these global settings.

It means that this one site that we found 10 years ago is not just an odd outlier. It means it’s representative; it’s the tip of the iceberg in terms of this phenomenon.

And what we also found at this site was that the water, having sat in these deep rocks for so long, can have reactions with the rock itself; these reactions can generate resources which are important for both humans and for smaller life and microbiology as well. It can produce things like helium and hydrogen. These findings have been studied and documented before. We know that, but what we had evidence for now is that this groundwater is not only producing radiogenic elements, such as helium, neon, argon and xenon, but also an unprecedented discovery of the isotope krypton, a never-before-seen tracer of this powerful reaction history. These radiogenic elements are also escaping from the rock. So they’re spreading out into other parts of the (Earth’s) crust. And this means that they have the potential to act as power generators in the deep crust on a global scale.

The groundwater could be supplying helium, which society needs for many things like the medical industry, for welding, and lots and lots of applications. But it’s running out and we don’t really know exactly the generation and accumulation mechanisms. So this is kind of critical for understanding how helium as a resource can be formed and migrated. Also, if other radiogenic elements like hydrogen could be migrating, well, this can sustain life completely away from the sun. So you can have biomes and biosystems and other life forms operating in the deep subsurface on billion year time scales as well. It’s got the potential for that as well.

Dr. Oliver Warr collection groundwater sample by Dr. Oliver Warr - University of Toronto
Dr. Oliver Warr collecting groundwater sample, Courtesy: Dr. Oliver Warr - University of Toronto

ON: Wow! That’s amazing. So my next question: is there any significance to the fact that the water is billions of years old? Can younger water serve as well?

OW: So with water, like with rock, to get these kinds of reactions the environments are typically very old and so you can get these processes to occur over very long time scales.

It’s not a flash in the pan sort of thing. It’s more about the longevity. The fact that these regions have been serving as these kinds of power generators over billions of years, that’s really exciting to us. I think the other key point, which we touched upon a little bit in the press release at least, was that as long as you have water in the presence of rocks, then you do get these kinds of reactions.

And so that means that it doesn’t necessarily apply only on earth. If we think a little bit further ahead, I’ve been looking at the surface of Mars; it looks a bit dry. There’s a potential that there could be water trapped underground in Mars as well in similar type of settings that are in cracks and fractures in the rocks underground. And so in these cracks and fractures, you would be getting the same generation of helium and hydrogen. So there’s the potential of energy production there. Now, obviously, we don’t know anything at all about any life or any potential life there, but this would be an energy source, which is fantastic, but it means it doesn’t have to be tied to the dry surface.

ON: It seems that the driver of this process is radiation and so the question becomes, I’m not a geologist, so I don’t know, but I seem to remember reading that radioactive elements came from the asteroid field or asteroid belt and are not actually indigenous to earth. Maybe that’s true. Maybe it’s not, but the question is if you were to look for life elsewhere in the solar system, you would have to find places (planets or moons) that have radioactive elements in their crusts. And how is that distributed throughout the solar system?

OW: That’s a fantastic question! So it turns out that these things are indigenous to rocks in the entire solar system. When rocky planets and everything formed, they actually did contain a small amount of uranium, thorium, potassium, and lots of other elements as well. It’s not restricted to any part of the solar system.

So these elements are spread out in low levels in most rock types, to be honest. And this is not just on earth, but other kind of rocky situations as well, like Mars and beyond, really. These are very low level concentrations, but when you have billions of years, they can actually generate significant amounts of these elements, like in the form of hydrogen, helium, etc.

ON: So do you think our own moon could have this process running?

OW: That’s a very good question. So you can get uranium, thorium decaying and that just produces helium, so you don’t even need water for that. It’s when the decay of uranium, thorium, potassium interacts with water, the energy causes it to split apart. And that involves creating the hydrogen. The abundance and the nature of water on the moon is something colleagues of mine are actively researching. As long as there is water as liquid or ice trapped in the subsurface, then there’s no reason to think it wouldn’t happen.

ON: So the groundrock is the source of the radiation and the radiation is breaking apart the H2O molecules into hydrogen and oxygen.

OW: Right. And that’s where the hydrogen, helium, neon are coming from. And presumably oxygen as well now. The oxygen is likely to react with the rock itself and it causes additional reactions which can create more elements and compounds, which life can potentially live off of as well. This is something else that we’ve been working on.

ON: So my other question is why did you pick a mine for your research? What are the characteristics of such a place that led you to conduct your research?

OW: We’ve been working on that mine for quite a long time. And by we, I have to give a lot of credit to my colleagues in Princeton as well as New Mexico and at Oxford and in South Africa. And obviously my PI professor because they have all been investigating mines around the world over many decades.

So we’ve been characterizing the environments and the water and the rock on a global scale there. And through these long interactions, we find that there is particular evidence that suggests the water might be really old. And one of the best ones is the composition of the gas which comes out because when you’ve had rocks and water interacting over billions of years, then you’re going to be producing a lot of gases.

And so you can actually fairly straightforwardly sample these gases and then analyze them. And if they’re rich in things like helium and hydrogen, you can say this is evidence that there’s probably long-term processes occurring. And so then you can carefully collect the gases, can measure them, and then you can determine a more accurate age; work out how long the water has been trapped underground.

Dr. Oliver Warr collection groundwater sample by Dr. Oliver Warr - University of Toronto
Dr. Oliver Warr collecting groundwater sample, Courtesy: Dr. Oliver Warr - University of Toronto

ON: That’s fantastic. So I’ve got another question for you. I’m going back to something you said that understanding the process of where helium and hydrogen is being generated could be useful for humanity because we’re running out – how would we exploit this knowledge? I mean, it seems like it’s a natural occurring process that takes a long time probably to generate useful quantities of these elements. So how could we exploit this for our own gain?

OW: First of all, that’s a fantastic question and we’re still very much in the exploration phase. On that question, we would need to find a place where these elements are being produced over these long time periods. Potentially, geologic settings and structures where they could accumulate. So think of it like hydrocarbons, you know, natural gas, oil; they form somewhere, they migrate and then they get trapped and the same would be true for helium as well. And so we’ve now started to understand a bit more where helium is being generated.

And now we’ve got evidence. And the next step would be to see where it accumulates and gets trapped. So, you need to have an understanding first of where it is generated, how long it’s been generating, and the volume.

You’ve got to know where to look. And then once you’ve figured that out, you can drill down there and suck it out. But if the groundwater is not very old at all, or it looks like it’s lost all its helium and there’s nothing, that’s not going to be a good place to be looking for helium.

You could find a place where it’s been produced over very long time periods and then it might have a chance to form significant volume so that it becomes an economic resource, because if it got spread out throughout the entire crust, that’s not necessarily going to be that useful. It needs to have a trapping and focusing.

ON: Right. It is very much like natural gas. Do you think there’s any reason to expect that it might have a greater concentration? Or do you think it’s more evenly distributed across the crust?

OW: I think, honestly, it’s a little bit too early to tell because we need to understand these systems a little better to understand exactly the rate of production versus release versus accumulation.

And that means a detailed understanding of the geology at a whole range of depths as well. So we need to characterize it a lot better. But that’s not to say that we haven’t got sites where we have a good understanding of this. It’s still very much in the early stages as it were, but we are running out of helium. So this needs to move really.

ON: Where did those radioactive elements come from originally if they are not indigenous to earth or other celestial bodies?

OW: I love this part of the story actually. If we go all the way back to the Big Bang which took place 14 billion years ago. Right? So when the Big Bang happened, then the main elements which were produced in that were only hydrogen and helium. All the other heavy elements came afterwards. So for our particular solar system, the working model is that there was a previously really big sun that formed from some of these elements. An absolutely massive sun. Then this sun went supernova and when it went supernova, it was hot enough and the pressure was high enough to actually produce all the other heavy elements, including the uranium thorium, and others. Then, when this really massive sun exploded, it created all these elements. And then this is where our own sun then formed the earth, the moon, Mars, etc. We all came from this second phase. That’s why these radioactive elements all spread out already in the solar system, because it was there during this massive explosion. It is amazing that suns are creating all the heavy elements and all the heavy metals. And so everything that we see on the earth was formed in the explosion of a star. The time scales on this is just amazing.

ON: Previously you mentioned that the gas would be the first clue for you to pick a spot? Are there other clues for you to pick a location for research?

OW: That is correct. The other clue is something I’ve not talked about so much: the fluid. The water itself should be extremely salty. It could be eight times saltier than sea water as well. That’s because the water, which has sat there for billions of years, has had these billions of years to react with the rock and exchange irons and become saltier. These really old fluids are typically very salty because that’s just what happens when you leave water trapped in a rock for billions of years.

ON: How does your research change our understanding of the origin of life on earth?

OW: One theory is it came from outer space. Another theory is that it may have originated deep in the crust. What we find is that there’s the ability to sustain life.

But the question which is still very much an open question is where did the life originally come from? Because we’re not able to say with any certainty, whether life formed on the surface and went underground, or whether it could theoretically have formed underground and then come out onto the surface.

I don’t think we’ve got enough information to answer the question. We just know that life can be sustained underground at least. What would you need to do to answer that question? This is a little outside of my field, but this is something that many of my colleagues and dear friends are working on and they’re trying to work out exactly what you need for life to form and what the likely environments are.

Life on earth has been around for 3.8 billion years or so. I’d have to look up the actual current working date, but the conditions on earth, both above and underground, 3.8 billion years ago are potentially very different. And so we can’t just assume that the current settings can be easily copy-pasted back billions of years.

Part of the struggle actually is trying to understand what the environments were like that could have been conducive for life and where they could have been.

ON: Sounds great. What’s your next step in this research?

OW: There are different potential avenues. I’m still very keen to understand how the geochemistry of these deep subsurface environments evolves over

time and what they can tell us about potential habitability models away from the surface and that’s my driving focus now. Elements in the subsurface can tell us about long term geologic processes. That’s the other strand of my research.

ON: Intuitively, the radioactive elements seem harmful to life forms but from your research, they are actually the generation for life.

OW: I think the easiest way of thinking about this is that there’s kind of a background radiation almost everywhere, all the time. And if it’s at really low levels, it’s never a problem. The levels of radiation that you find in these rocks that we’re talking about are so low that actually, it doesn’t matter. It doesn’t cause damage; it’s not like walking into a nuclear reactor amounts of energy. But what the subsurface lacks in high concentration it makes up for in volume and time.

To actually generate these elements, even just walking around, we are being constantly bombarded at very low levels by solar radiation, but our bodies can cope with that. And it’s the same in the subsurface, but actually at even lower amounts of energy being created, it’s just that it can accumulate and be generated on such big volumes that then it matters at that point.

It’s like picking up a rock. It is not going to do anything except maybe make your hand hurt after a while. But when you leave that rock for a billion years, it might produce a good amount of hydrogen and helium.

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With much gratitude, we wish great success to Dr. Warr and his colleagues in their research in understanding what is happening deep down in our earth.