The Mariana Trench's Challenger Deep—the deepest point on Earth—looks as bleak and barren as the moon, according to James Cameron, who successfully returned just hours ago from the first solo dive to the ocean abyss.

At noon, local time Monday (10 p.m. ET Sunday), the National Geographic explorer and filmmaker's "vertical torpedo" sub broke the surface of the western Pacific, some 200 miles (322 kilometers) southwest of Guam.

After a descent that took roughly two and a half hours, Cameron spent about three hours conducting the first manned scientific exploration of Challenger Deep.

For his return trip, Cameron experienced a faster-than-expected, roughly 70-minute ascent, which he described as a "heckuva ride."

Bobbing in the open ocean, his custom-designed sub, the DEEPSEA CHALLENGER, was spotted by helicopter and plucked from the Pacific by a research ship's crane.

The expedition was designed so that Cameron could spend up to six hours collecting samples and video at the bottom of the trench. But his mission was cut short due in part to a hydraulic fluid leak that coated the window of the sub's "pilot sphere," obscuring his view.

"I lost hydraulics toward the latter part of dive, and I was unable to use the manipulator arm," Cameron said this morning during a post-dive press conference held aboard the Octopus, a yacht owned by Microsoft co-founder Paul Allen, a longtime Cameron friend. (Allen was on the scene for the historic dive and posted live updates of the event on Twitter from aboard his yacht, which provided backup support for the mission.)

Considering the daunting task of sending humans into the deep, such technical glitches are to be expected, Cameron emphasized: "It's a prototype vehicle, so it's gonna take time to iron out the bugs.

"The important thing is that we have a vehicle that's a robust platform—it gets us there safely, the lights work, the cameras work, and hopefully next time the hydraulics will work."

And although he wasn't able to capture as many samples on this first dive as science teams might have been hoping for, "that just means I gotta go back and get some more," said Cameron, also a National Geographic Society explorer-in-residence.

In fact, he and sub co-designer Ron Allum, managing director of the Australia-based Acheron Project research and design company, already have more dives planned in the coming weeks as part of the DEEPSEA CHALLENGE project, a partnership with the National Geographic Society and Rolex. (The Society owns National Geographic News.)

"I see this as the beginning ... of opening up this frontier to science and really understanding these deep places," Cameron said.

Little Life Found in Challenger Deep

Aboard the DEEPSEA CHALLENGER, Cameron had a host of tools at his disposal, including a sediment sampler, a robotic claw, and temperature, salinity, and pressure gauges. (See pictures of Cameron's sub.)

The sub is also outfitted with multiple 3-D cameras and an 8-foot (2.5-meter) tower of LEDs.

But in part due to the hydraulics leak and a host of lost thrusters, Cameron wasn't able to capture any biological samples, and an attempted sediment core sample was only partially retrieved.

"I didn't see big jellyfish and big anemones like I saw [during test dives] at the New Britain Trench," off Papua New Guinea, Cameron said. (See "Giant 'Amoebas' Found in Deepest Place on Earth.")

At Challenger Deep "I landed on a very soft, almost gelatinous flat plain. Once I got my bearings, I drove across it for quite a distance ... and finally worked my way up the slope."

The whole time, Cameron said, he didn't see any fish, or any living creatures more than an inch (2.5 centimeters) long: "The only free swimmers I saw were small amphipods"—shrimplike bottom-feeders that appear to be common across most marine environments.

"When I was in the New Britain Trench a couple weeks ago, the bottom was covered in the tracks of small animals, which gave it an eggshell appearance," he added.

"But when I came to Challenger Deep, the bottom was completely featureless. I had this idea that life would adapt to the deep ... but I don't think we're seeing that."

Still, the science team is hopeful that the small sample Cameron took of the trench's sediments, along with the sub's constantly whirring cameras, will provide some new insight into the remote underwater realm. (Video: How sound revealed that Challenger Deep is the deepest spot in the ocean.)

"Jim recovered about 50 milliliters of muddy seawater that I gleefully processed for culturing and for genomic studies," Doug Bartlett, chief scientist for the DEEPSEA CHALLENGE project, said in an email to National Geographic News.

"Can't wait to see what new critters (Bacteria, Archaea, and fungi) that we discover," said Bartlett, a marine biologist at the Scripps Institution of Oceanography in San Diego, California.

The mud could contain exotic species of microbial life that may not only advance our understanding of the deep ocean but also help in the search for extraterrestrial life.

For instance, scientists think Jupiter's moon Europa could harbor a global ocean beneath its thick shell of ice—an ocean that, like Challenger Deep, would be lightless, near freezing, and home to areas of intense pressure. (See "Could Jupiter Moon Harbor Fish-Size Life?")

Deep Dive was Like a Trip to Another Planet

Until Cameron's dive, the only manned Challenger Deep expedition was a mission that took place in 1960, when retired U.S. Navy Capt. Don Walsh and late Swiss engineer Jacques Piccard descended in the Navy submersible Trieste.

Climbing into the cockpit of DEEPSEA CHALLENGER, Cameron said he was "intimately aware of the design of the vehicle ... and I felt we'd done the engineering right.

"When the hatch closed, I felt the vehicle around me was able to withstand the pressure. There may be butterflies in your stomach beforehand, but once you're inside the sub, the excitement of going someplace [few have] been before takes over ... the adrenaline takes over, and the fear really goes away."

Cameron also had to overcome the sheer physical experience of the dive—the 57-year-old explorer was crammed into the sub's 43-inch-wide (109-centimeter-wide) pilot sphere, which itself was loaded up with navigation controls, cameras, and other electronics.

"I wind up packed in like a Mercury astronaut, if you will," Cameron said. (Video: how the sub sphere protects Cameron.)

"When you first close the hatch, all these electronics are dumping heat into the sphere." Since the Mariana Trench lies near the Equator, surface temperatures are high, and the inside of the sub's cockpit "gets very hot right away—it's like a sauna inside.

"But as you start descending, the sub goes very fast. I'm screaming down, and in just a few minutes I'm in water that's 36 degrees Fahrenheit [2.2 degrees Celsius].

"All of sudden my feet are freezing, the back of my head is freezing, but the middle part of my body is still warm," he said.

Then, "literally within a minute or two I'm out of sunlight, and you're in total darkness for most of this dive, so the sub gets very cold, and you have to put on warm clothing. ... The walls have condensation all over them and I'm constantly getting dripped on by cold water."

Despite the physical challenges, Cameron seemed in awe of what he'd experienced in the remote ocean depths.

"This is a vast frontier down there that's going to take us a while to understand," he said. "The impression to me was it's very lunar, very isolated. I felt as if, in the space of one day, I'd gone to another planet and come back."

Hoping for Gifts From the Ocean

According to biological oceanographer Lisa Levin, of the Scripps Institution of Oceanography in San Diego, California, the DEEPSEA CHALLENGE program's potential for generating public interest in deep-ocean science is just as important as anything Cameron might have discovered.

"I consider Cameron to be doing for the trenches what Jacques Cousteau did for the ocean many decades ago," Levin, who's part of the team but didn't participate in the seagoing expedition, said in a previous interview with National Geographic News.

At a time of fast-shrinking funds for undersea research, Levin said, "what scientists need is the public support to be able to continue exploration and research of the deep ocean."

Perhaps referring to his friend's most recent movie, expedition physician Joe MacInnis called Cameron a real-world "avatar."

Cameron was "down there on behalf of everybody else on this planet," MacInnis said. "There are seven billion people who can't go, and he can. And he's aware of that."

Camron added, "Every time you dive, you hope you'll see something new—some new species. Sometimes the ocean gives you a gift, sometimes it doesn't.

"But I call this dive just the first phase. We prove that the vehicle works, and hopefully bring some real science back."

Ker Than and Rachael Jackson, of National Geographic Channels International, contributed reporting to this story.