|The oceanography of the Challenger Deep|
Graphic from CNN.com here
It has only been visited once before by humans when Navy Lieutenant Don Walsh and the Swiss explorer (deceased) Jackques Piccard rode in their submersible, Trieste, to its bottom. In their descent, the outer layer of their porthole cracked when they were about five miles down, and still a mile above their destination. The Triest was the first wholly self-contained submarine to make the venture. It was a giant, cigar-shaped "balloon" filled with 22,500 gallons of petrol--which is lighter than water--to provide buoyancy. Beneath this ballon was a tiny steel sphere, 7 feet in diameter, holding the two adventurers. It had nine-tons of iron pellets attached to make it sink. These were then jettisoned on the ocean floor.
There is apparently a high-competitive race going on between Cameron, who has been preparing for this rather secretly for five years, and Richard Branson, who has built an airplane-shaped Virgin Oceanic submarine. The third competitor is Patrick Lahey, the president of a small Central Florida company, Triton Submarines. Cameron's submersible is being built by Australian engineers, and the goal is to film in 3D at the bottom.
Why the race? $10,000,000 will be awarded by the X-Prize Foundation, a nonprofit organization that aims to inspire radical breakthroughs that will benefit humanity. The Deep is 35,814 feet below the ocean surface, a mile deeper than Everest is high.
What's so exciting about the Challenger Deep? For biologists, it's the possibility of documenting some of the estimated 750,000 species of marine life that we haven't found yet (and this excludes the billion estimated unidentified microbes).
According to a 2010 article in the DailyMail.co.uk, Cameron plans to film parts of an Avatar sequel down there. Let's hope that he's successful!