Awesome Jobs: Meet Nathalie Cabrol, Planetary Scientist and Extreme Altitude Diver

By Erin Biba

Nathalie Cabrol, a planetary scientist at NASA, climbs some of the world’s highest mountains and dives into their lakes to understand what life on other planets may have been like in the past before climate change eliminated their surface water.

Nathalie Cabrol is a planetary scientist at NASA Ames and a senior research scientist at the SETI Institute. But just because her research focuses on the geology, ecology, and history of faraway planets doesn’t mean she stares through a telescope all day. On the contrary, Cabrol holds the world record for the highest elevation dive by a woman. And she got her record in the name of science! Cabrol climbs some of the world’s highest mountains and dives into their lakes to understand what life on other planets may have been like in the past before climate change eliminated their surface water. Cabrol sat down to chat with us about her legendary dive in the Andes and how we can learn about other planets by studying our own.

Free diving in a lake located at 8,000 ft as training for the Licancabur expedition.

How can you study Mars from Earth?

My field is on Mars. So that makes it a big commute to get there. So I chose to go, not exactly halfway, but I climbed some way towards it.

If you want to go to Mars, you want to know what is the environment in the past and was it suitable for life? I have to go to Mars analog environments. The higher you go on earth, the thinner the atmosphere is, the more UV, and the temperature changes are the same as they are on Mars at the equator (even today). A volcanic environment is a good analog.

This is what drove me to climb the high volcanoes in the Andes. I was interested in the combination of extremes. I am a lake person. My husband and I have been promoting the idea that there were lakes on Mars. Nobody had thought about the fact that water could have pooled. Once the idea was OK in the community, we went to those very high volcanic lakes to try to understand what the environment would have been like.

What does it take to get to the bottom of the lake at the top of a mountain?

Not being afraid to put a foot in front of the other. For a long time you have to think only about that and not about the goal which is the summit. Those are very high climbs -- 20,000 foot high mountains. In the Andes climbing to 20,000 feet you have all the mountain gear on you, it’s cold, you have to get acclimatized, you go with your colleagues, and when you get there they have become your friends too.

The year where we did our diving expedition we carried 500 kilograms. That’s half a ton of equipment and we were traveling light. Believe me, we had the most competitive diving equipment possible. It was very light.

You must have been a very adept diver...

I am a freediver. Normally I would dive without any breathing apparatus. I don’t have any specific issues at all with altitudes, so I didn’t feel going to the Andes was more difficult then to freedive than at sea level. But you have to be more careful. You don’t want to surface with your lungs empty because you only have half of the atmosphere to breathe up there. I realized very quickly I would not be able to document that lake if I was freediving.

[When altitude diving] you don’t want to surface with your lungs empty because you only have half of the atmosphere to breathe up there.

Freediving sounds terrifying. And you’re just doing it for fun?!

I once did that with Scott Parazynski, he’s a shuttle astronaut. We did a freedive together and when we got to the surface, I said: “Scott, how would you rank this out of 10?” and he looked at me and he said: “20!” This is coming from a guy who has been flying six times on the shuttle!

So had you ever done a Scuba dive before your Andes trip?

What I did first to prepare for the expedition was I finally certified Scuba. I am fearless. But there is one thing up to that point that I couldn’t get over and that was a pressurized vessel. I had that irrational fear of pressurized vessels, and this explains why I didn’t certify before. There was really no reason. I’m not the type of person that’s afraid. I had the answer one day talking to my mom serendipitously. She said: “You want me to explain to you why you’re afraid?” She said when I was less than a year old I was playing in the kitchen and the pressure cooker blew up and the lid flew one inch above my head. It was traumatic. I have no recollection of it, but I kept the fear. I’d see a gas tank or anything under pressure and I would make detours.

From that point on I was able to rationalize my fear. Pressurized vessels are much better now and the chances that it’s going to happen again are really small.

So I took on scuba diving.

Nathalie training in the Catalina Islands, CA with the CODE Rebreathers, August 2006.

You must have had to train pretty intensively, then, since you didn’t have much experience with Scuba...

Diving at this elevation has all sorts of concerns. You don’t want to dive with conventional air, you can get a bubble of air in your system and you can die. At 20,000 feet when you’re isolated that’s a very bad idea.

So we started talking about diving at 20,000 feet. It was clear that if people weren’t using rebreathers and pure oxygen we were going to get the bends. A year before at dinner I had met Dominique Sumian -- the chief expedition leader for Jacques Cousteau. I actually learned to freedive in the south of France in places he knew. I contacted him at that point and he said "come to San Diego with your team and we’ll certify you with military rebreathers."

That was perfect. It is really like a light backpack, with a scrubber. The civilian version would have done the trick, but it is three times heavier than this one. Now that we were training and getting certified and AquaLung was generous enough to loan us this equipment for our expedition for free.

What, exactly, is a rebreather?

We used the standard diving gear that you would use in the ocean. But the tank is the heaviest. The regular Scuba is a tank that you put on your back, attached to your floatation jacket, and you also have the lead belt. The rebreather is a bag containing a C02 scrubber that cleans the air you’re breathing and recycles it. So you don’t have any bubbles coming out. It’s a small bag: one foot by one foot. You have this tiny, tiny tank of oxygen that you’re breathing from and everything goes in the front, you have nothing to carry on your back, which gives you more mobility and freedom of movement.

Because of the elevation we needed a lot more lead than you would with the wet suit. I had about 40 lbs of lead and I’m 126 pounds. You can imagine how uncomfortable I was on land.

Because of the elevation we also had a dry suit and we needed a lot more lead than you would with the wet suit. I had about 40 lbs of lead and I’m 126 pounds. You can imagine how uncomfortable I was on land.

So what was it like, once you finished your training, to finally get up to top of the mountain and dive?

Diving there was an incredible experience. I came from being a pure freediver in June 2006 and being at the summit in November and doing this dive, which is still the highest dive in the world. For a woman I have the record.

Climbing those mountains is dangerous but not technical. It’s dangerous because it’s on loose rocks, big boulders, and they’re unstable and the earthquake risk is worse there than here in California.

You have to be resilient and resistant. It takes time. We have a camp at midslope and then a summit camp on the outer site of the crater. The volcano is dormant but not not extinct.

Once we arrived we had two dives we needed to do. We were three divers and a dive master and medical support on the shore. The first day I was taking samples and the other two divers were doing photography and video. I feel so comfortable in the water -- I feel more comfortable inside then out. But before I entered the water that day I was nervous. You train for three months and I spent so much time in the swimming pool at the bottom, I said you better give me a phone line at the bottom of the pool. If you want to find me, you’ll find me there. We had rehearsed everything. We had devised an interesting way of diving there because when you have a rebreather you don’t have any bubbles so people at the surface don’t know where you’re. It’s not safe.

What we did was something that solved a number of issues. Each of the divers had a float on top him or her. A buoy. Inside was a net with a GPS unit whose clock was coregistered with the clock on the camera we were holding down below and the bathymetric map we had completed the day before. Whenever we collected a sample, only by looking at the time stamp on the photo we would know exactly its coordinates and its place on the map.

We had a line from the buoy that was attached to our lead belt and we were repelling up and down the line so people on the shore knew where we were at all times. We could ascend easily and also attach a lot of equipment on the line with carabiners. So it was a mixture of climbing and diving.

The second day we made a transact of the lake and sampled for microbiology, for soil, and water chemistry. That day I was holding the camera. I was able to sit back and relax.

What did it look like?

The lake was completely transparent. Arctic blue. I photographed the rays of the sun piercing the water one by one.

It was a little over 5 meters deep [Editor: 16 feet] -- that’s an upgraded swimming pool.

Nathalie last training in full gear and video camera before the dive at Licancabur in November 2006.

I was suspended there filming panoramas and I was able to think about where I was. “OK lady, you’re at the summit of a volcano which is not exactly extinct on a very high mountain in the water in a diving suit.” I thought, if that thing blows up I’ll be the first diver in orbit. I’ll still have my breathing tank and a decent suit so maybe I can just wait to be picked up like a hitchhiker.

You completely lose the notion of time. This sense of being weightless. Everything was light. The sun diffracting in the water. It was just amazing.

You completely lose the notion of time. This sense of being weightless; despite all the lead, I didn’t feel it too much. Everything was light. The sun diffracting in the water. It was just amazing. It was literally out of this world.

But not. We learned a lot about the potential for life on Mars and its resistance to a high UV environment. I also was able see how this lake was changing so fast year by year and then it hit me that if this lake was showing me what Mars would have been like millions of years ago, it was also pointing to what was happening here and now on earth. That’s when I decided to push my research in parallel between life on other planets and climate change on our planet.

Did you have any trouble surfacing in the low atmosphere?

The NASA review board was concerned that after breathing pure oxygen for a while we might pass out after removing our rebreather. We’d be breathing an atmosphere that has much less oxygen. So we transitioned to medical oxygen for a little while.

We used so much energy the second dive. Each of us sucked up two tanks. We were high on oxygen! We broke camp inside the crater, broke the summit camp, and ran down in two hours. This is what too much oxygen will do to you.

But we didn’t pass out. With so much oxygen in our system it was hard to go to sleep.

How long did you spend diving?

The first dive we stayed down 25 minutes and the second dive was closer to 40 minutes. At this altitude that’s not a short dive. The second dive I was very, very comfortable. But one of my companions started to get cold. If one diver is not 100% you all go up. I was still filming them going up and then I realized they were going up but I was comfortable. And then I said: “You better get the hell out of here!”

Why do you have to do such a short dive when you’re up that high?

The first thing is that the water is 4 degrees C, that’s 37 or 38 degrees fahrenheit. That’s really, really, really cold. We have good clothes and we can fight hypothermia, but the cold temperature is one of the main drivers. You don’t want to start to get cold, you want to get out before that, because by the time you’re cold it’s too late. It’s interesting because I was never cold in the lake. But a few years ago I was diving in another lake, much lower, around 10,000 ft. The water was 12 C or 13 C and I was freediving for 1.5 hours--that requires a lot more energy because you have to go up and down. After an hour and 31 minutes I started to feel a little cold in my hands. Two minutes later it started bother me a lot and a minute later I needed to find a quick exit. I went in three or four minutes from feeling fine to saying: “OMG where’s the nearest exit?” When you start getting cold it’s too late.

Second, you don’t want to be exhausted. A rebreather is an interesting exercise. It’s a different beast. The mouthpiece can be a little hot. But you don’t want to be exhausted when you come to the surface because you need to spend energy getting to shore in an atmosphere that has half the normal pressure. And you only have 48 percent of the oxygen. In the Andes, by the time I got to the surface my rebreather mouthpiece was so hot I got rid of it and then I started swimming. But that was a huge mistake. Sprinting at this elevation is not a good idea. By the time I got to shore I was so exhausted I couldn’t pull myself out. I was on the shore and they dragged me a few feet. I had 40lbs of weight around my waist and that didn’t help. You’re not in your natural environment. At 20,000 feet no human being can live. There is no adaptation to very high elevation. That’s what we start calling the death zone. There are a number of reasons why you have to be more careful.

Could we expect a similar experience from putting humans on Mars?

We wear suits and are breathing oxygen so we were separated from the outside environment. This is the analogy. We dealt with that mission like a flight mission. We had an experimental protocol and we trained for many months. You see the divemaster going through the checklist and then you hear “Go!” It’s the real deal. We were looking at each other in the water for the first five minutes. I never checked my equipment so often in my life. But something caught my eye and got my attention, something I took a sample of, I saw the goal of our mission right there and forgot everything about the cumbersome aspect of the mission. Everything was fluid. We had done it over and over again in the swimming pool.

In that respect that was exactly like what an astronaut would do before a mission.

So, you’ve done this amazing dive and learned a ton of things about Earth and how Mars used to look. Where do you go from here?

I want to do more. Climate change and global warming are creating lakes even higher. I’m trying to get back there.

In the meantime I have a number of projects. I have one in the central Andes at a lower elevation. This one is to test technology and systems for exploring the lakes of Titan for a future mission. We’re developing a robot and floating platform. The question is: how do we explore alien lakes and seas remotely? We have lots of experience with rovers, but no robots that go on the water.

We’re developing a robot and floating platform. The question is: how do we explore alien lakes and seas remotely?

This is a project that, at the same time, allows us to approach exploration strategies of alien lakes and seas for Titan. We perform it in places being affected by climate change, which allows us to bring data supporting the study of climate change on Earth, but by the same token gives us information about what could have happened on Mars 3.5 billion years ago in analog environments, when the climate changed on the red planet. That’s a threefold project.

This is where the experience of the lakes we visited before in the Andes allows us to see differences in the deglaciation phases (the loss of ice due to global warming). First, you increase the amount of melt -- lots of ice is melting. You have more discharge in runoff, you’re eroding a lot more material because you have more power and energy in the stream, thus you bring more sediment into the lakes. The second phase is you melt so much ice that glacial streams have less discharge. All the sediment that was brought in before starts to settle down at the bottom of the lake. It’s a complete ecological catastrophe for the species in the lake because the lake becomes more transparent. More UV penetrates and the species that are not protected against them disappear...

Later, when glacial melt input stops, if there is no spring or precipitation, then the lake starts to evaporate. The lakes we’re studying in the high Andes are very far along in this process.

But in the Santiago areas in the central Andes it’s starting to happen right now.

Meanwhile, we also learn about what could have happened on Mars in similar conditions in the past, when Mars still had glaciers. We want to learn all the reasons why this is happening and the signatures of turbidity and temperature changes. In terms of robotic missions, these two parameters are relevant to Titan, not because of deglaciation but just because this is what happens in lakes: temperature and transparency change.

When I keep dry we’re doing the same thing in the desert, but with a rover. This is an application to a possible future mission that will be searching for life on Mars. We’re trying to build the right tools to detect subsurface life.

I have to ask, why explore the Earth and not attempt to become an astronaut yourself?

The more we learn about Mars the more we see the similarities with Earth and the potential for life to have evolved and still be there.

I wanted to be an astronaut, definitely. It’s the space program that died on me not the other way around. At the same time, there is also a multistep vision. There is a point in time when you say: “OK, let’s go there.” We did that for the moon. The more we learn about Mars the more we see the similarities with Earth and the potential for life to have evolved and still be there. It is extremely important that we do a very thorough job at understanding whether life is there or not. It should be done without human interference. We’re a microbial factory. The day we put a human on Mars we will find life on Mars. We should make a concerted and thorough effort to address that question. And we haven’t started yet. We’ve only addressed the habitability aspect -- and we have proven without a shadow of a doubt that it was, and still could be, habitable for microbial life as we know it. That’s why putting a human there would be a problem at this stage. We still need to complete that step of at least trying to find life and we haven't. VIKING wasn’t a rationalized try. The results are still very ambiguous today. Curiosity is not looking for life, it’s looking for the presence of organics. It cannot, unless a rabbit is jumping in front of the camera, find life.

We still need to put that mission or those missions at the surface of Mars before we can send a human. When that time comes I’ll be too old to be an astronaut. And I am fine with it. Because I don’t mind being a stepping stone on that process. I try to understand how to help finding this evidence of microbial life on Mars. In that sense, I am helping make steps towards the human exploration of Mars. The sooner we find these little critters (or have made or peace with the fact they might not be there), the sooner we can send a human crew. And this prospect is exciting. Meanwhile, we are learning a lot about our own planet by going to impossible places that we wouldn’t go to if not to understand some other fancy planet in the solar system. This is SO worth it. This is such an incredible journey. I’ll be an astronaut in my next life.

Not all science is done in a lab by guys in white coats staring into microscopes. Lots of discoveries require brave men and women to put their boots on the ground and get down and dirty in dangerous environments. Every month we’ll profile one of these field scientists, tell you how they do their job, and explain the science behind what they do. If there’s a scientist or field of science you’re dying to hear more about shoot us an email or a tweet: erin at erinbiba dot com, @erinbiba