Editor’s Note: This article is the first of a two-part Q&A from a roundtable in which James Cameron discussed deep-ocean science with researchers at the Woods Hole Oceanographic Institution in Cape Cod, Mass.

In March filmmaker and aquanaut James Cameron, back from his record-setting visit to the Challenger Deep in the Marianas Trench 11 kilometers below the surface of the Pacific Ocean, announced the donation of his sub, DEEPSEA CHALLENGER, to Woods Hole, where scientists plan to use its cutting-edge technology to help further their understanding of life in ocean trenches.

The first order of business when the DEEPSEA CHALLENGER arrives at Woods Hole in a few weeks: Fit its custom-made lights, imaging equipment and high-definition 3-D cameras on to Woods Hole’s Nereus robotic sub in preparation for the latter’s dive to the 10-kilometer-deep Kermadec Trench—off the northeastern tip of New Zealand's North Island—in February or March 2014. The Kermadec Trench is a kilometer shallower than the Challenger Deep site that Cameron explored, but Nereus’s mission is crucial to understanding the peculiar inhabitants, ecosystem and geologic activity that have evolved in ocean trenches—the planet’s most hostile habitat.

The roundtable discussion with Cameron took place in New York City in April and included: Tim Shank, a Woods Hole deep-sea biologist and lead investigator for the institution’s Hadal Ecosystem Studies (HADES) program; Andy Bowen, director of Woods Hole’s National Deep Submergence Facility; Susan Avery, president and director of Woods Hole; along with a handful of journalists.

In part 1 Cameron and the Woods Hole researchers talk about how the technological advances that enabled the DEEPSEA CHALLENGER to take him to the deepest spot on the planet will unlock new possibilities for understanding life at the vastly unexplored hadal depths, those below six kilometers. The discussion also addresses the upcoming Nereus mission and what Woods Hole hopes to find at the bottom of one of the world’s deepest, coldest trenches. Cameron also describes his experiences piloting the DEEPSEA CHALLENGER on his historic voyage to Challenger Deep in the Mariana Trench.

In part 2 Cameron discusses how the era of exploration in the 1960s—both into space and to the ocean’s depths—inspired his career as a filmmaker and, later, as an deep-sea pioneer and science advocate.

[An edited transcript of the interview follows.]

Why are you donating the DEEPSEA CHALLENGER to Woods Hole?

James Cameron: To me, that’s an infinitely better outcome than it sitting dormant until I’m done with my next two movies, and maybe comes to the tech community five or six years down the line when it’s already obsolete or other solutions have been found in the meantime.

[When the dust settled following the March 2012 piloted expedition to the Challenger Deep] my fantasy goal was that the entire scientific community would want to have access to it. Unfortunately the kind of money that existed in the 1960s and ‘70s, the heyday of deep-sea exploration, is harder to come by these days. So we had to look for a way the technology could be beneficial to the oceanographic community. And we came up with something that we’re all happy about.

In terms of [future missions for] DEEPSEA CHALLENGER, I don’t think that any of us want to take that off the table. We’ll look at possibly getting it out to sea again at some point and go out and try to find some funding for that when it makes sense. The more immediate goal is to transition technology from the sub into the mainstream of the oceanographic community.

Short of taking the DEEPSEA CHALLENGER out again, how will it benefit deep-ocean science?

Andy Bowen: That’s underway right now. Some of that technology will be transitioned into our Nereus underwater robotic vehicle, which will undertake a scientific survey project in the [Kermadec Trench] using, in particular, the cameras developed as part of the DEEPSEA CHALLENGER program.

Cameron: It’s interesting how those cameras came about. We knew the DEEPSEA CHALLENGER was going to move through the water column rapidly so we would have as much bottom time as possible. But that meant if we wanted to have the camera out on a boom to be able to see the sub and the area around it, that camera was going to be tiny, and I wanted high-definition and 3-D [capabilities]. My previous HD [or high-definition], 3-D submarine camera weighed about 180 pounds, and it went on a 150-pound pan-and-tilt mechanism. Well, all of that was going to have to go out on a boom, and that clearly wasn’t going to happen on a small weight- and space-constrained vehicle.

So I set my engineers with the challenge of coming up with something that was orders of magnitude smaller and had to operate twice as deep as our previous camera system. That puts you off the scale in terms of difficulty, but they built the camera from the sensor level up. [Two of these cameras in a titanium housing weighed about four and a half pounds] We put it on a four-pound pan-and-tilt platform. You could put a couple of these on Nereus.

What else will Woods Hole do with the DEEPSEA CHALLENGER when it arrives in June?

Cameron: My team of engineers that spent seven years building the DEEPSEA CHALLENGER will share their experiences and knowledge with Woods Hole engineers, and vice versa.

I don’t expect a fleet of DEEPSEA CHALLENGERs to be built. That was a very specific vehicle that served a very specific purpose. But if you were able to take the various systems on the sub and abstract them out to a different form factor, you might end up with some of that being integrated into an [autonomous underwater vehicle] for hadal research. Several of those out there going through the trenches starts to give you much better science in return.

I haven’t put any constraints or restrictions on [how the DEEPSEA CHALLENGER’s technology is used]. I think we agreed not to saw up the sub for awhile.

What are the specific scientific goals of the 2014 expedition to the Kermadec Trench?

Tim Shank: We want to take Nereus on a six-week expedition to the Pacific Ocean’s Kermadec Trench to explore part of the ocean’s hadal regions, which are largely unknown. The vast majority of information about these regions comes from two cruises in the 1950s [the Danish Galathea and the Soviet Vitjaz expeditions], which is rather embarrassing. We just have a catalogue with the names of some species that came up in a trawl. In the 2000s there were a couple of cruises that explored hadal depths and brought back some samples, each of which is incredibly valuable. [Sediment samples from the Mariana Trench, for example, have contained highly active bacteria communities even though the environment there is under extreme pressure almost 1,100 times higher than at sea level, according to a March Nature Geoscience report.] The research [also] showed a carbon food supply down in the trenches that we hadn’t known about. [Scientific American is part of Nature Publishing Group.]

There are seven institutions around the world and 10 scientists [involved in the Kermadec expedition as part of the Hadal Ecosystems Studies (HADES) program] who are out to answer six major questions, including what’s there in terms of biodiversity, what they are feeding on and how they’ve evolved in isolation.

Cameron: I think it’s interesting to have an overview of just how little is known about hadal depths in terms of biology and geology. Most of what’s known about the bottom has come from images shot miles up in the water column, and it’s a relatively coarse data set. So you’ve got to get down there and look around and ground-truth it. Very little of that looking around has been done. As Tim said, there’ve been a couple of cruises.

Shank: Foremost, we want to bring back samples and study their use for biotechnology. Based on the hadal samples we’ve seen so far, these animals secrete enzymes that are very beneficial for humans. Some are being used for trials to treat Alzheimer’s disease. Now we’re looking for antibody, anticancer, anti-tumor properties, too. All of this depends on how well you can preserve these animals and bring them up [alive], something we can’t do now. [Living samples have been brought to the surface successfully from no deeper than about 1.4 kilometers.]

Cameron: Their biology just doesn’t work when that pressure is taken away. But the deeper you dive the less equipment you can bring with you. It would take a heavy piece of gear to bring a pressure vessel down to hadal depths [that could keep specimens alive when they are brought to the surface].

To the best of our knowledge right now, what is life like at the bottom of the trenches?

Shank: People think the trenches are these ponded settlements, but they’re very dynamic places. There’s a lot of friction and fracturing that goes on [on the ocean floor]. There’s a buildup of sediments and water gets squeezed out of those sediments, and that percolates up and interacts with rock. Lots of earthquakes, and that means a lot of slopes [on the ocean floor]. We also think that there are mud volcanoes in these trenches, sediments that build up over time with their own unique chemistry.

With the HADES program, we’re trying to study every 1,000 meters down to the maximum of 11,000 meters. We think the trenches are completely different from the rest of the ocean. The paucity of the food source on the seafloor for some reason increases when you get to the trenches. It’s less and less and less until you get to the abyssal plane. Then, when you go deeper, the available food source increases. We don’t know why that is. Maybe it’s the topography of the trenches bringing that stuff in. Whatever it is, we think that’s supporting the great diversity in the trench habitat. But it’s hard to learn those kinds of things if you just send down a drop-camera system.

Cameron: There’s a reasonable hypothesis that [geologic activity in hadal zones] might be the crucible for life, and that needs to be looked at.

Bowen: It’s almost like you’re looking back in time. The trench is a window into [biological and geologic] processes that we have not been able to witness.

Shank: The microbes [from hadal regions] we’ve looked at so far are very diverse. They have a multitude of functions, and [they survive on chemicals including] methane, hydrogen and sulfide. Some of the arthropods down there have cellulose-digesting enzymes in their bodies. They can digest wood. Other animals show signs of gigantism [they’re inexplicably bigger than their shallower water counterparts]. One theory is that you’re so deep you can’t fold your proteins because your cells are too squished. You have to have a way of making yourself larger, and you have specialized enzymes that do that. Another theory is that you have to make yourself bigger to function, and we know they have the enzymes to do that. But you can’t be gigantic if you don’t have a big food source, which is another indication there’s a lot of food down there, much more than we thought. There are so many exceptions to every explanation that nothing has worked yet. Way more questions than answers.

Ocean exploration has been underway for decades, why is it still so difficult to study life in the trenches?

Cameron: We’re right at the cutting edge of hadal-depth technology. Everything changes when you go below 6,000 meters. [From an engineering perspective] at that point, your performance–benefit ratio has changed in terms of flotation, pressure vessels, wall thickness and so on. Vehicles tend to get very heavy and unmanageable. That drives up your power budget and your cost, and it’s not a trivial problem. People think that because you can get to four miles down, that extra three miles shouldn’t be a big problem. But you come up against the limits of materials science where you actually have to create new materials to create vehicles that have the same agility and cost factors as ones that operate higher in the water column. Which is why hadal depths are still relatively unexplored.

Your success as a filmmaker has been tied to deep-sea exploration, starting with The Abyss and continuing with Titanic and the documentaries about making that movie. How did you prepare for your dive to the Challenger Deep?

We developed the [DEEPSEA CHALLENGER sub] in Sydney and then we were going to dive it essentially near Guam at the Challenger Deep. We wanted to prove the sub could reach that spot in the ocean, not necessarily because the deepest spot is the most scientifically interesting place but because once you’ve demonstrated that you can go anywhere else. In the process of getting to Guam, the Tasman Sea [got to be] quite rough. So we started looking for a deep place we could operate near a landform that would prevent the propagation of the big oceanic swells that are driven by the trade winds at that time of year. We looked between the New Britain and New Ireland islands, where the New Britain Trench [runs] five miles deep, plenty deep enough for us to do our sea trials before we went on to the Challenger Deep.

It was meant to be technical sea trials, and we had a whole science team that was meant to meet us in Guam from Scripps, the University of Hawaii, and even the University of Guam and Jet Propulsion Laboratory—people that I knew. It turned out there was so little data about what’s at the bottom of the New Britain Trench, they all wanted to come early and take a look at that. So our sea trials actually ended up being science dives, where we were bringing back samples, which is fine because we needed to have an activity to focus on anyway.

Can you describe your historic dive to the Challenger Deep?

Cameron: I doubt my pulse went up much. Maybe when we took away the floats [at the surface]. I was task focused. I had a multipage checklist that was organized around time and depth, metrics, things I had to do. I had to power up systems in a certain order because the sphere would overheat. One of the biggest problems with the sub is the heat flux. The pilot’s sphere is very tiny, and it’s got a lot of equipment packed in there with me. If I turned all of the equipment on at the surface, I’d bake. I’d literally be like poached salmon. So I had this whole protocol for bringing things online as needed. The unique thing about the Challenger Deep dive is that I got through everything on my checklist that had taken me right down to the bottom of the New Britain Trench, then I had nothing to do. And I had 9,000 feet to go.

I had a little stereoscopic HD camera out on the end of a two-meter boom. I would just point the camera across at a spotlight I left on. And the spotlight would illuminate the particulate in the water column. I got to the point where I could tell in half-knot increments what the [plankton] particulates running through the spotlight would look like if I was going fast or slow. When I got below 29,000 feet, my altimeter just stopped. The “snow” went away at 29,000 feet, and the [altimeter] reading went to zero. The water was just clear.

Going down, I left the surface at 5.2 knots and arrived at the bottom at zero basically. The first thing I saw when I landed was the track of some other vehicle, which might have been [Woods Hole’s Nereus, which had been to the Challenger Deep in 2009]. You get away from that one [landing] spot, and there’s really almost nothing. You don’t see how the animals are behaving when they’re alive in situ.

Why is deep-sea exploration so important to you?

Cameron: It’s good to remember that the aggregate area of these hadal trenches is greater than the size of the United States, greater than the size of Australia, so it’s basically like a continent that’s never been explored that exists right here on Earth. So many people think we live in a post-exploration age—it’s all been seen, it’s all been mapped. How did we manage to get into the 21st century and just happen to miss a continent? Because that’s what we did. The answer is obvious: It’s the hardest place to get to on the planet. From a technological standpoint, it’s the most challenging place to operate. I would make the argument, having been involved with space robotics and now full ocean-depth technology, it’s a much more demanding environment than building hardware for space because the stress forces are so much greater, about 1,000 times as much.