Over the weekend, James Cameron successfully made it to the the bottom of the Mariana Trench—the deepest point on Earth. Bad. Ass.
But also: lucky, brave, well-prepared, and maybe a little bit daft: Any number of factors could have turned the the veteran explorer-slash-director's epic adventure into his last act.
The Mariana Trench is located in the western Pacific Ocean, to the east of the Mariana Islands. It's over 1,580 miles long, 43 miles wide on average, and and at it's deepest point—heroically known as Challenger Deep—it's an amazing 6.78 miles to the bottom. Almost 36,000 feet. Reaching those depths is incredibly dangerous, and James Cameron himself is alleged to have admitted that the mission offered "a lot of ways to die." So what could have gone wrong?
The obvious, quickest, and most catastrophic route to failure. A weak spot in materials, a design flaw in the vehicle. Then, as the pressure increased—pop—the dive craft would have buckled. That doesn't mean drowning; it means James Cameron would have been squashed to death, with immense pressures of up to 15,750 psi turning his body into a James Cameron slurry.
If the Deepsea Challenger, had somehow gotten stuck at the bottom of the trench, Cameron would have been relying on his life support systems to keep him alive. In terms of resources, he had 60 hours of oxygen—but far less in the way of power for heating. With the water of the Mariana Tench being a fairly consistent 0°C, he would have died of hypothermia long before he ran out of air.
The sub was packed full of technology and gadgetry—all requiring electricity. There was also a vast amount of pure O2 circulating around inside Deepsea Challenger. The tiniest of electrical faults or sparks, and that O2 would have had a fire burning hard and fast. There was a small fire extinguisher on board—but it might not have stood up to something major.
Even though the Mariana Trench is cold, it's surrounded hydrothermal vents—fissures in the Earth's surface from which geothermally heated water bursts, unannounced. Thing is, that water is incredibly hot—700°C to be precise. That's hot enough to melt the submarine's view port. Then Cameron would have had water issuing into his craft, driven by 15,750 psi of pressure. Game over.
Though you might not realize it, the sea bed—even the area surrounding the Mariana Trench—is littered with submarine communication cables. They're there to string together telecommunication systems around the globe, but also turn the bottom of the sea into an assault course for submariners. If Cameron had gotten tangled in one of those lines, he would've struggled to make it back to the surface.
Fortunately, Cameron was one lucky mother; he managed to make it down and back up without a hitch. Which is fortunate for us, because no doubt his footage from the alien-esque world of Challenger Deep is going to be freakin' amazing. Congratulations, James.
Image by Mark Thiessen/AP