Mars Rover, Move Over: Making A Rover To Explore The Deep Sea

17:15 minutes

A collection of machinery parts and wheels that sits on the bottom of the ocean.
Benthic Rover II travels across the muddy seafloor, taking photographs and measuring how much oxygen bottom-dwelling animals and microbes are using over time. The information gathered by this autonomous rover has helped scientists understand how carbon cycles from the surface to the seafloor. Credit: © 2016 MBARI

When you hear the word ‘rover,’ it’s likely your brain imagines another planet. Take Mars, for instance, where the steadfast rolling science labs of Perseverance and Curiosity—and the half dozen robotic rovers before them—slowly examine the geology of the Red Planet for signs of past habitability.

A purple fish glints in slight light as it swims close to the sand at the bottom of the ocean.
The camera on Benthic Rover II captures its fleeting encounters with fishes on the abyssal seafloor. Rattails (Coryphaenoides sp.) are scavengers that swim in the waters just above the seafloor, searching for food.
Credit: © 2021 MBARI

But Earth has rovers too. The autonomous, deep-sea Benthic Rover II, engineered by researchers at the Monterey Bay Aquarium Research Institute (MBARI), trawls a desolate surface too—this one 4,000 meters below the surface of the ocean, on a cold abyssal plain, under the crushing weight of 6,000 pounds per square inch of pressure.

Deep beneath the surface, the rover is seeking data about carbon: What carbon sources make it down to such a deep sea floor? And does that carbon return to the atmosphere as carbon dioxide, where it might contribute to global warming, or sequestered safely as an inert part of the ocean sediment?

Ira Flatow talks to engineer Alana Sherman and ecologist Crissy Hufford, both of MBARI, about the work it takes to make a rover for the deep sea, and the value of its data as we look to the future of our oceans.

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Segment Guests

Alana Sherman

Dr. Alana Sherman is the electrical engineering group lead at the Monterey Bay Aquarium Research Institute in Moss Landing, California.

Crissy Huffard

Dr. Crissy Huffard is a senior research specialist and ecologist at the Monterey Bay Aquarium Research Institute in Moss Landing, California.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. When you think of a rover, I bet your mind lands on Mars, right? Dusty red rocks and the noisy horror of the wheels of a rolling laboratory slowly, patiently examining a strange planet to understand its past. Well, I do when I think of it.

But did you know that we have rovers right here on Earth? 4,000 meters, that’s about 2 and 1/2 miles below the surface of the ocean, exploring the depths of an abyssal plain is one such rover, the Benthic Rover II. And it’s not looking for signs of past life. No, instead, it’s looking for data that might tell us about our future on a warming, uncertain planet.

Here with me to talk about this deep sea explorer and the work it’s patiently doing year after year after year are my guests, Dr. Alana Sherman, head of the electrical engineering group at MBARI. That’s the Monterey Bay Aquarium Research Institute– and Dr. Crissy Hufford, senior research specialist and ecologist at MBARI. Welcome to Science Friday.


CRISSY HUFFORD: Thanks for having us.

IRA FLATOW: First of all, tell us what this rover looks like Alana.

ALANA SHERMAN: Well, the rover is about the size of a small SUV, and it’s a tracked vehicle like a tank. So it has two treads, one on each side of the rover, and it has these large titanium spheres that are about 17 inches in diameter. And those spheres, there’s three of them on the rover, and they carry the electronics and the batteries for the rover.

And then it has flotation, which helps the rover not be too heavy underwater, and that flotation actually, it looks like plastic. And it’s a type of foam, but it is very solid. And so it’s brightly colored so that, when the rover comes to the surface, we can see it at surface.

IRA FLATOW: Yeah, it’s good to have that. Crissy, when I looked at it, it looked to me like that cartoon WALL-E a little bit. Do you anthropomorphize it to look like people.

CRISSY HUFFORD: We do think of it as a pretty charismatic team member in the lab, and we do definitely notice that it has these little foam packs right in front that look like eyes. So we add a little human nature to it.

ALANA SHERMAN: We used to joke that the rover was my baby because I worked on it for so long, and then I had two non-robotic babies. And I realized that it was by far my most– my one child that actually did what I said to do. [LAUGHS]

IRA FLATOW: And it’s rolling around on the sea floor. Give us a little mental picture of the abyssal plain environment, where it is, what surrounds it. Crissy.

CRISSY HUFFORD: So the abyssal plain covers a very large portion of our Earth. The Benthic Rover II operates at the base of a feature called the Monterey deep-sea fan, where that meets the abyssal plain. And the abyssal plain on Earth is a big, expansive, muddy, open, relatively flat habitat compared to what we’re used to seeing on land.

IRA FLATOW: And what kinds of stuff is down there? What kind of cool stuff does it see?

CRISSY HUFFORD: Well, our idea of what’s charismatic really changes based on the habitat we’re looking in. In the deep sea, we have many animals that deep-sea ecologists consider pretty charismatic. We have swimming sea cucumbers. We have very large-eyed fish. We have squat lobsters or little crabs that have little spiky projections all over them. It’s a really different set of animals compared to what we’re used to seeing in shallow waters.

IRA FLATOW: And Alana, is this an easy environment for a robot or not? Two and a half miles down, there’s tremendous water pressure and all kinds of stuff that it could get into trouble with.

ALANA SHERMAN: It is a very challenging environment for a robot in many ways. You name the pressure, which is true. The pressure and the sea floor where we operate is 6,000 pounds per square inch. You also have the corrosive effects of seawater, and it’s also very, very cold. So these are all challenges that, taken together, are hard to replicate in the lab, so it makes for the need for doing very robust engineering to make it out there for a year at a time.

IRA FLATOW: Would you say it’s more difficult to engineer this than, maybe, one of the Mars rovers?

ALANA SHERMAN: Well, I don’t want to say that because I think there’s a whole slew of challenges involved in making the Mars Rover. But they do have the advantage that they can communicate with it daily, and they could potentially interact with the software there whereas, once we deploy our rover for a year, we have very limited communications and no way to really– very little ways to change what it’s operating.

IRA FLATOW: Oh, is that right? So it’s like– it’s really a robot. It’s autonomous. It’s not like you have a little hand controller that you’re working two and a half miles above it.

ALANA SHERMAN: We often debate whether we should make a little robotic hand in there that can press buttons, but we haven’t gotten to that point yet. But it is truly autonomous. The most we could do is we occasionally send another autonomous robot to check on our autonomous robot. This is a surface vessel that can go there and speak with it acoustically, but that’s a very limited bandwidth. And it also does not work very well in heavy sea states.

IRA FLATOW: Mm-hmm. And Crissy, what is its mission? What is it doing down there? What is it collecting? What is it learning?

CRISSY HUFFORD: So the Benthic Rover’s core mission is to help us understand how much carbon is being consumed in the deep sea, and so it does this with little respirometry chambers that measure oxygen draw down. And from that, we can calculate carbon consumption. But one of the advantages of the rover is that it also has the space to put on other types of sensors and other ways of collecting the data and understanding the deep sea, so it has cameras, a fluorescence imaging system. It has a current meter.

And with these other data sets, we’re able to get a pretty decent picture of what’s happening down there. We can tell when lots of food is coming down. We can tell when the animal community changes through its pictures of the sea floor. And we can tell the influence of these changes in the carbon cycle on changes in things like, for example, oxygen concentration in the nearby waters. This time series is over 30 years old, and every time we bring the instruments up, we find something completely new.

IRA FLATOW: Not stuck to the instruments, I’m guessing.

CRISSY HUFFORD: No, luckily not.

IRA FLATOW: And why are robots better than people to do this kind of research?

ALANA SHERMAN: Well, it would be very hard to have a person, living, resident at 4,000 meters, walking around, taking measurements with an oxygen sensor, so robots are able to endure in these environments, like the Mars Rover, that are hard for people to exist in.

IRA FLATOW: And Crissy, tell me about what you’re really trying to understand. You said something about you’re trying to understand the carbon cycle in the oceans. Why do you need to know that? What is the ultimate bit of knowledge you want to grasp here?

CRISSY HUFFORD: So as we know, humans have put a lot of carbon dioxide into the atmosphere, and a big question that scientists have, generally, is, where does that carbon go? And the ocean takes up a large amount of that carbon dioxide. 25% of the carbon dioxide we’ve put into the atmosphere has been taken up by the ocean. And a lot of that makes its way into the deep sea, and if carbon makes its way to the deep sea in a way that it won’t exchange again with the atmosphere anytime soon, that can qualify it as deep-sea carbon sequestration.

So when the deep sea takes up carbon, it pulls it away from the atmosphere where it won’t warm us and continue to do the harm that we think of as associated with climate change. So we’re measuring how much carbon makes its way to the very deep sea, 4,000 meters depth, which is the average ocean depth. And we’re also interested in what happens to that carbon once it gets there. Does it get consumed right away? Which is what the Benthic Rover tells us. Or might it actually– might some of it be stored in the sediments over longer time periods?

In the surface waters, phytoplankton can take that carbon dioxide and turn it into food. When that food sinks, it brings that carbon down as food to the deep sea, which is an important base of the food chain down there. And when the food is eaten in the deep sea, the microbes and organisms, animals down there take in that food, and they respire carbon dioxide down there. And that dissolves into the seawater, and it makes the seawater acidic down there.

So the deep sea is experiencing ocean acidification just like the surface waters are. We’re trying to figure out how much of that carbon makes its way down there and what its role is ecologically, whether it gets eaten right away or it might get stored in the sediments.

IRA FLATOW: Would it be possible to sequester extra CO2 we have above the surface deep down there?

CRISSY HUFFORD: Well, the big challenge is doing that in a way that doesn’t harm deep sea ecosystems, and if we dump lots of carbon into the deep sea in any way, shape, or form that could be treated as food, then that carbon will be eaten. And that will be released into the deep sea as carbon dioxide, and it will acidify our deep ocean. It will also take up lots of oxygen, and so that will de-oxygenate our deep ocean and potentially lead to dead zones. The times when we see some carbon might be stored in the sediments, that’s just periods when there’s so much coming down in these very brief what we call pulse events that the animal and microbial communities can’t keep up, and there’s a little bit left over.

IRA FLATOW: And these pulse events are happening why?

CRISSY HUFFORD: Good question. We think this is traced back to what’s happening in the surface in our climate. As the land is heating up more, it’s driving stronger seasonal winds off of our shores, which is driving stronger upwelling and phytoplankton growth in surface waters, and that just brings more food into the ocean. And some of that makes its way to the deep sea. But what exactly determines how much of these pulse events make their way to the deep sea we still are trying to figure out.

IRA FLATOW: Interesting. The bottom of the ocean, the deep parts of the ocean, we’ve said for many years that we know more about the surface of the moon, maybe now about the surface of Mars, than we know about the bottom of the ocean. Do either of you ever feel a bit like you’re helping explore another planet? Or does it feel unfair to compare the oceans to another planet or to the moon?

CRISSY HUFFORD: For me, as a biologist, I don’t think of this as this alien habitat, these alien life forms. I think of them as my neighbors. I’m closer right now to a whale or some of these deep sea animals than I am to a grizzly bear, our state animal. And so I feel very linked to these animals through my actions and through what happens in the climate and the surface waters, and what I do can you address– one out of every four breaths that I exhale are taken up by the ocean, and some of that carbon from me might make its way to the deep sea.

IRA FLATOW: Wow, I’ve never heard that explained quite like that. Alana, what about you, other planets or the ocean?

ALANA SHERMAN: Oh, well, I would say the ocean, personally. Unlike Crissy, I don’t know if I feel like it’s another planet, but it is definitely so right for exploration and discovery. As Crissy said, every time we bring up the instruments, we find something new. It is stuff we’re finding that’s relevant to our existence. I find that is very motivating. And it’s fascinating on so many levels. Biologically, the chemistry, the geology, all of it is pretty exciting.

IRA FLATOW: This is Science Friday from WNYC Studios, talking to Alana Sherman and Crissy Hufford about sending rovers to the bottom of the sea. If you had a blank check, which I had back here in my pocket if you can reach it, and you could use it to build instruments or to do something with it to answer questions that you can’t now answer, build a new kind of robot, Alana, what would you do with it?

ALANA SHERMAN: When I first started my career, someone suggested that the ideal would be a robot that could follow a piece of marine snow from the surface to the seafloor, and I think that’s a goal we’re still kind of working towards. So I would build an autonomous underwater robot that had the ability to track an object, whether it was marine snow or an animal, and be able to stay with it for long periods of time.

A lot of the questions that we try to answer in the ocean require, just like the rover does, the sustained observations. Otherwise, you miss the most important thing, like the pulses that Kristi mentioned. If the rover wasn’t there all the time, we would miss these pulses that may only be a few days out of a year, and that’s true of other phenomena in the ocean.

IRA FLATOW: OK, now, Crissy, Alana has decided to share her blank check with you.


CRISSY HUFFORD: And I absolutely love what Alana has chosen to do with that blank check because I share that same desire for sustained tracked observations. And so many of the questions that we have about animals in the deep sea and ecosystems relate to time. The Station M time series has given us this long perspective of how climate has changed the deep ocean, and the next questions we have are, how and through what mechanisms? But we’re even trying to get at basic information like, how long do animals live? We don’t know that for almost all deep sea organisms, and the technologies that Alana described would help us get at that.

IRA FLATOW: And you also have a lack of people knowing what you’re actually doing down there, right? Everybody sees pictures from Mars and the rovers. We don’t see much coming up from the ocean bottom in your rovers or any kind of exploration, deep-sea exploration, until somebody sends something to the Titanic or something like that.

ALANA SHERMAN: I think that the ocean provides– from an engineering perspective, I think it provides a lot of really interesting challenges, and I certainly, when I was in engineering school, did not know about this area of engineering. And I think, from a science perspective, it’s very relevant to our lives, and I think it’s so ever present that maybe we kind of forget about it.

IRA FLATOW: Alana, what got you into this kind of engineering in the first place, sending scientific instruments into the ocean?

ALANA SHERMAN: Well, I really wanted to build scientific instruments, and I thought that maybe that would mean working in some biotech laboratory or something like that. But I had heard about MBARI. That really aligned with my desire to use engineering towards making scientific discoveries. But I never stepped foot on a boat until my first week here, and that was an exciting day, too, which I don’t have time to tell you about.

IRA FLATOW: We don’t have time for it either. I’m sorry. We’ve run out of time. I want to thank you both for taking time to be with us today.

CRISSY HUFFORD: Thanks for having us.

ALANA SHERMAN: It was our pleasure.

IRA FLATOW: Dr. Alana Sherman, head of the electrical engineering group at MBARI, the Monterey Bay Aquarium Research Institute, and Dr. Crissy Hufford, senior research specialist and ecologist at MBARI.

Meet the Producers and Host

About Christie Taylor

Christie Taylor was a producer for Science Friday. Her days involved diligent research, too many phone calls for an introvert, and asking scientists if they have any audio of that narwhal heartbeat.

About Ira Flatow

Ira Flatow is the host and executive producer of Science FridayHis green thumb has revived many an office plant at death’s door.

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