The Lost City

Where life on Earth began, with Dr. William Brazelton

by Alli Hoffman

The Lost City of Atlantis supposedly existed somewhere between 10,000 and 11,000 years ago. But it was much later in human history, 1978 to be exact, that a group of scientists discovered nature’s version of the mythical city sitting right beneath our noses. Well, 2,500 feet beneath the surface of the Atlantic Ocean. You won’t find mermaids or other fabled creatures roaming this Lost City; instead, a system of towering deep-sea hydrothermal vents teeming with otherworldly lifeforms and complex microbial communities.

Perhaps a more fitting name would be the “Garden of Eden,” given that scientists like Dr. William Brazelton, microbiologist, oceanographer, astrobiologist, and research investigator at the Blue Marble Space Institute, believe these vents, or others like them, to be where life on Earth first emerged in microbial form from the dark, sunless depths of the deep blue 4 billion years ago. It’s thanks to the lifelong work of Dr. Brazelton and scientists like him (and some robots named Alvin and Jason) that we know what's down there in the first place. Not just for the sake of exploration, but for the sake of understanding how life got a foothold on our pale blue dot.

The expert himself gave us the rundown on why this ecosystem might just hold the primordial blueprints for the origins of life and how it can inform the search for extraterrestrial life. Equally, if not more important, the Lost City redefines how we position life, and ourselves, on the grand timeline of our world and that of our universe. After all, Sir David Attenborough said it best: “If life can exist under such extreme conditions down here, then surely it could exist somewhere out there."

Flow Trip: Tell us the origin story of how the Lost City was first discovered?

Dr. William Brazelton: Hydrothermal vents in general were only discovered in 1977 or 1979, so it's a relatively recent discovery. Most of the ‘80s and ‘90s were spent doing a lot of geology to understand how these seafloor spreading systems work, which was happening along the Mid-Atlantic Ridge. As part of that research, the scientists more or less accidentally mapped what we would later call the Atlantis Massif — an underwater mountain that, even later, the Lost City would be found on top of.

In 2000, there was an expedition to study this mountain and to understand the geology, because they thought there was a good chance that this giant mountain was composed primarily of mantle rocks (rocks that had recently been in the mantle and had floated up to the surface as a result of the sea floor spreading apart). It's not that common that you can get rocks that were recently in the mantle. And as a part of that, they had this towed camera — a robot-looking thing that's attached to the boat with a data cable and a tether with a bunch of cameras mounted on it. During the day, they would go down in Alvin, the manned submarine, to look at the mountain and collect samples and do geologist things. At night, they would tow this camera around to get more data and footage of the sea floor, which is usually a super boring job. So imagine they’re sitting there looking at the monitor, and out of nowhere they see this white ghostly spire show up when they were not expecting to see anything there at all, let alone hydrothermal vents. 

Hydrothermal vents are right where the sea floor spreads apart, and you get magma and really hot fluids seeping out from underneath the sea floor. But these ones were on this giant mountain, about 15 kilometers away from the center of the sea floor spreading. It was quite a surprise when they saw this show up on the video camera. They went there with Alvin the next day to collect the first samples.

FT: Why did it end up being called the “Lost City”?

WB: The Atlantis Massif was named because it is on the Atlantis Transform Fault. So the Mid-Atlantic Ridge is not quite a straight line, but all of these zigzags, which are transform faults. They called this zigzag the Atlantis Transform Fault because they named it after the ship that they were on, which was the US research vessel Atlantis. So the ship was called the Atlantis, the transform fault was called the Atlantis, and the mountain was called the Atlantis Massif. Then someone said, “Why don't we call it the Lost City? Because it's on Atlantis, and these tall chimney-like spires kind of look like skyscrapers?” And some of the tallest ones are about the size of a skyscraper. It really is like a little city down there.

FT: Explain in terms a third grader would understand why it’s believed that hydrothermal systems like the Lost City are where life on Earth began?

WB: Life, as we know it today, eats other life. When we eat food, we're eating the products of other life forms. But the very first life form on Earth couldn't eat other life because it was the first one. The only thing that it could have eaten was non-biological, or non-living fuels like carbon dioxide. That's what plants do, right? They turn carbon dioxide from the air into food. So that's one part of the whole; that the first life on Earth was turning carbon into food. To do that, you need a source of energy. The two options for the source of energy are from the sun or from inside the Earth. That's one reason why it’s believed that hydrothermal systems like the Lost City are where life on Earth began: They're the place where we have lots and lots of energy from inside the Earth being focused into one spot, that doesn't depend on the sun.

The second reason is that these hydrothermal vents actually make organic compounds without life. So not only do they provide energy for turning carbon into food, the hydrothermal vents themselves will actually convert carbon into a food source without the help of life. They were already making a lot of the ingredients you need for life before there was ever any life. We still don't understand many of those steps between non-life and life, but at hydrothermal vents, we can at least start to see little glimpses of how we might start going in that direction before there was life on Earth.

FT: Why do we see such unique and odd creatures at these hydrothermal vents?

WB: One reason is that the environmental conditions down there are so different from what we're used to. Instead of photosynthesis, where you have a community driven by the sun and green plants, you have chemosynthesis, where life is being driven by energy from inside the Earth. For that reason, lots of things end up being different. There are clams that are entirely built from the food made by the bacteria inside their digestive systems, and the bacteria inside them depend on sulfur from the hydrothermal vents. It's just a completely different way to form an ecosystem compared to what we're used to on the surface. That's one of the things I am most excited about with hydrothermal vents, that it's basically alien life on our own planet. It shows that there is more than one way to make an ecosystem. And I find that really inspiring.

FT: Could you elaborate on that more — that this is basically alien life on Earth, and why, as a scientist, that is so exciting?

WB: In biology, you learn that the base of the ecosystem is green plants turning carbon into food from the air, building their biomass, and then humans and other animals eat the plants, and that's how you make an ecosystem. And when astronomers are using telescopes to look for life on other planets, they're looking for green stuff, or photosynthesis, because if you looked at Earth from a long way away, that's the first thing you would notice — it's a planet with a big ocean and a lot of green stuff on land that could be life. What you wouldn’t know about Earth is that it also has a completely different kind of ecosystem at the bottom of the ocean that has nothing to do with the sun and is instead all connected with energy coming from inside the planet. And so now that we know about hydrothermal vents and that they support a different kind of ecosystem, when we look for life on other planets, we can think about that as another way to support life. We don't really have an easy answer for how you would look for that kind of life, because it would be hard to detect it, even on our own planet. But it's an important thing to keep in mind that you could have a planet completely full of life that is not green and does not have a perfectly warm sun nearby.

FT: Why is this research impactful to how we understand the origins of life on our planet? How is this intertwined with the search for life on other planets?

WB: If we're right that the chemical reactions occurring between these sea floor rocks and water are making some of the ingredients for life, that is actually really exciting — because there's nothing super special about those rocks. The rocks where these reactions are taking place are rocks from Earth's mantle. Earth's mantle is huge, and it's representative of the other rocky bodies in our solar system. While Earth's crust, like our continents and our sea floor, might be special, Earth's mantle is just like that of other planets. So if it's true that this kind of rock that makes up the mantle will make ingredients for life if you give it water, that means there's the potential for making the ingredients of life almost anywhere where you have rocks and water. From that perspective, I think [this research] is super important for understanding if the origin of life was either some lucky accident that just happened in one spot, or a natural consequence of the interaction of geology and water.

FT: What do you think the importance is of continuing to explore and protect these unseen ecosystems — the Lost City and others like it?

WB: The main thing I would highlight is how little we know about the sea floor. It's a cliche now, but it's also true that people often say that we know more about the surface of Mars than we know about our own planet, because our ocean makes it very difficult to study the sea floor. You can't see the sea floor by using satellites. The only way you can study the sea floor is to take some sort of submersible down there. Because of that, it's always going to be slow, it's always going to be difficult. And right now, there's a lot more money being invested in using the sea floor as a resource for mining rare Earth metals to turn into batteries than there is for scientific exploration. We are really worried that we're gonna turn some of, or a lot of, the sea floor, into batteries before we even know what is there in the first place, because the way you mine, you don't have to see where you're going. That’s the urgency right now, is that we at least need to find out what's down there before we start crunching it all up. But it doesn't have to be a complete either-or. There are many intermediate positions of “Let's explore the possibility of using the seafloor as a source of resources, but it can be balanced with doing it intelligently and not in a completely chaotic way.”

FT: What significance does the investigation of the Lost City’s microbial communities have?

WB: There are many different levels to answer that question. There are lots of other examples of finding weird microbes and then using properties of those microbes to make some cool product that then becomes economically valuable. It's a similar argument to not cut down the rainforest, because the rainforest could contain all sorts of cures for diseases that we haven't discovered yet. Hydrothermal vents are very similar. If you include microbes, the microbiological diversity of hydrothermal vents is on the scale of what you'd find in rainforests. Therefore, the potential for discovering useful things is also high. 

Another practical thing is geoengineering. There's a lot of interest right now in carbon storage: taking carbon dioxide out of the atmosphere, turning it into a mineral, and storing it in the ground to reduce the concentration of carbon dioxide in the air to help combat global warming. By understanding how these microbes are doing that naturally at the Lost City, we can understand how to do it in an engineering way.

One more point is to understand the ocean ecosystem as a global ecosystem. Hydrothermal vents play a role in the general health of the ocean. The whole ocean circulates through hydrothermal vents over relatively short time periods. You can think of hydrothermal vents as the water filters of the ocean — the water gets scrubbed as it goes through hydrothermal vents every few 1,000 years or so. The health of fisheries in the ocean in some very big global sense is likely indirectly connected to how microbes and hydrothermal vents are working.

You can learn more about The Lost City with Sir David in episode 2, “The Deep,” of Blue Planet II.

All photos by S. Lang, U, of S.C. | NSF | ROV Jason | 2018 © WHOI