Film director and explorer James Cameron on Monday completed a historic solo dive to the Challenger Deep – the deepest spot in the ocean – aboard an oversized torpedo of a submersible that expedition scientists say could help open new opportunities for researchers to study some of the most remote places on the planet.
The pioneering design of Mr. Cameron's Deepsea Challenger, as well as those of other groups who plan similar manned deep-sea dives later this year, may lead to a new generation of manned and unmanned subs that could accelerate the pace of research generally, other specialists say.
Cameron returned to the surface at noon local time some 300 miles southwest of Guam after enduring nearly seven hours tucked in a cramped cockpit so small he could not fully extend his legs. He spent nearly three hours at the Challenger Deep itself, gathering 3-D video.
He also had planned to gather samples of rocks and marine life. But a hydraulic leak rendered the sub's mechanical arm and claw useless, he explained during a post-dive press briefing.
With no way to gather samples, a planned six-hour stay on the bottom was cut in half.
It took him just over 2-1/2 hours to reach the Challenger Deep and a mere 70 minutes to reach the surface once his time on the bottom ended.
While there, he says he took a page from astronauts' experiences and made sure he took time to savor the view – the otherwise deep, black water illumined by banks of LED lights along the sub's hull.
“I just sat there looking out the window, looking at this barren lunar plain and appreciating it,” he told reporters, following the trip, which was funded by the National Geographic Society, Rolex, and the Alfred P. Sloan Foundation.
More trips are in the offing this year by various groups aiming to take people into the Challenger Deep or other parts of the Mariana Trench. These efforts include Sir Richard Branson's Virgin Oceanic sub, which like Cameron's Deepsea Challenger, is a single-seater. Several of the marine scientists who have worked with Cameron also are working with Mr. Branson's group.
Life in the trenches
Although deep-sea trenches make up only about 1 percent of the sea floor, they are of keen scientific interest. They form as old, dense oceanic crust, long ago made by lava welling up along mid-ocean volcanic ridges, now is pushed beneath more-buoyant continental crust.
The process creates a long, canyon-like boundary. The Mariana Trench, for instance, has an average width of about 43 miles but narrows to a slot-like valley at the bottom, nearly 7 miles below the ocean surface.
With crushing water pressure – roughly 1,000 times air pressure at sea level – and temperatures hovering around freezing, the environment at the bottom of these trenches is home to an unusual assortment of creatures. Last summer, for instance, a team from the Scripps Institution of Oceanography in La Jolla, Calif., and the National Geographic Society found that a super amoeba – a single-cell organism measuring about 4 inches across – was inhabiting depths two miles deeper than previously believed.
The creatures, known as xenophyphores, also host a range of other, multicelled organisms.
Samples of trench communities have turned up a range of more complex creatures, including shrimp, fish, and soft-shelled snails uniquely adapted to their harsh home.
The sea floor Cameron saw, however, was barren, he told reporters. He said never reached a place that looked to host any interesting biology.
For the creatures that do live in the deep, researchers are trying to figure out where they get their food, as well as the pecking order in the food chain at such depths.
The region also is of interest to astrobiologists as they explore approaches to detecting and studying life on other planets or moons. Jupiter's moon Europa and Saturn's moon Enceladus are thought to have small oceans under their icy crusts. Any future mission to explore those oceans would require some kind of sensor package sent into the depths.
And there's plenty of ocean exploration to do on Earth, notes Bob Gagosian, president of the Consortium for Ocean Leadership, a nonprofit organization in Washington that focuses on building support for ocean research and ocean policy.
Despite some 200 years of oceanography, scientists have explored a scant 5 percent of the planet's oceans, he says. For him, Cameron's dive is significant for the spotlight the filmmaker's efforts are throwing on ocean exploration and for the technology the Deepsea Challenger exhibits – in particular the stunning speed of descent and ascent.
Contrasting the Deepsea Challenger with Alvin, the iconic three-person submersible operated by the Woods Hole Oceanographic Institution in Woods Hole, Mass., Dr. Gagosian notes: Cameron “got down there at about 11,000 meters in the same amount of time it takes Alvin to get down to 3,500 meters.”
Alvin is undergoing a refit that will substantially increase its operating depth, although not enough to enable it to reach the Challenger Deep.
But the design approaches used by Cameron's team and others, if proven robust enough, could be applied to a new range of manned and unmanned vehicles, Gagosian says. Speeding ascent and descent means spending more of a voyage's expensive ship time on the bottom gathering samples and images, rather than in the commute to and from the ship.
Other aspects of the Deepsea Challenger could be useful, too. Cameron's cameras are building a 3-D video of the features he saw at the bottom of Challenger Deep – a form of vision important for giving for gauging distances and spatial relationships. Chris German, chief scientist for deep submergence at Woods Hole, calls it three-dimensional context.
Robots are the future
Over the long-term, however, Dr. German says improvements in sub technology, sensor technology, and virtual-reality tools are likely to reduce the need for humans in the hull. Just as scientists are exploring the solar system with probes controlled from Earth, they could explore the deep sea from dry land.
German is no stranger to the value manned submersibles play in marine science today. He's overseeing Alvin's upgrade. But, he says, the vehicles Cameron and others are developing may represent an effective but final generation.
Robotic vehicles can scope out sites, conducting the surveys that will allow researchers in submersibles to zero in on sites they want to visit and from which they want to pluck samples. And in some cases, robotic subs are doing both the reconnaissance and the follow-up research.
In January, German says, he sent an expedition to explore the deepest known sites with undersea hydrothermal vents. The vents are associated with a feature south of Cuba known as the Mid-Cayman Rise. The cruise relied on the Nereus, a robotic sub that can be operated either via tether or autonomously. The cruise followed one in which other, smaller robotic subs did the up-close reconnaissance work.
Two robotic subs have also visited the Challenger Deep in the past two decades. In 1995, Japanese scientists used Kaiko, a remotely operated sub, to gather sediment samples and marine organisms. The craft made several more dives along the Mariana Trench, which includes the Challenger Deep, before it was lost at sea during a typhoon in 2003. In 2009, scientists gathered more samples using the Nereus.
These days, humans in the hull are most valuable when they come across something no one has ever seen before, German says. Nothing beats a human at seeing something for the first time and trying to make some initial sense of it. Cameron says more dives to the Challenger Deep will follow this one.
Still, within the next 20 to 30 years, undersea technology may advance to the point where humans remain on the ship or even at a mission-control center on land, and run an autonomous underwater vehicle adroit enough to gather the samples, carry a heavy load back to the surface, and has the vision that allows its human handlers to respond quickly to unexpected features or activity on the sea floor they are surveying.
The manned research subs coming on line this year “are entirely appropriate for this generation of researchers,” German says. “I very much doubt that in 30-odd years' time we'll be doing it again. I bet this is the last generation of human-occupied vehicles.”