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.