Early Monday 26 March 2012 local time, film director James Cameron became the third person to visit Challenger Deep, the deepest part of the ocean. It was last visited in 1960, by Jacques Piccard and Don Walsh in the bathyscaphe Trieste – see here. Challenger Deep is a slot-shaped depression in the floor of the Marianas Trench, is 10,898.4 metres beneath the surface of the sea, where the water pressure is 114,000 kPa (about seven tons per square inch).

Cameron made the trip in a submersible called Deepsea Challenger, which was developed in secret. Unlike the Trieste, it did not use gasoline for buoyancy, but syntactic foam. The trip took Cameron over two hours, less than half the time it took Piccard and Walsh to make the same journey. He remained on the ocean floor for three hours – and not the planned six due to a hydraulic fluid leak. The Trieste spent less than twenty minutes in Challenger Deep.

There is an X-Prize associated with Challenger Deep: $10 million to the first organisation to make two crewed descents. This does suggest Deepsea Challenger will make another trip soon.

The fact that a private individual has achieved this – and he wasn’t the only one planning to do so: Richard Branson has a submersible of his own – does make you wonder if the first trip to Mars will be funded by some starry-eyed multi-billionaire. In Terry Bisson’s Voyage to the Red Planet (1990), the first Mars mission was partly funded by a film studio, who wanted to make a movie there. The novel was intended as a satire, but it could be sadly prophetic.

This is not to belittle Cameron’s achievement – though, to be fair, it hardly presented any insurmountable engineering challenges. The Trieste made the trip more than half a century ago, and consisted of a hollow steel ball attached to a float filled with petrol. Its designer, Auguste Piccard (incidentally, Hergé’s inspiration for Professor Calculus), had started work on his first bathyscaphe in 1937, and the Trieste‘s keel was actually laid in 1953. Deepsea Challenger is a far more sophisticated vessel, but a descent to Challenger Deep could have been made any time during the past fifty years.

All the same, it’s pretty cool. Though I doubt we’ll ever see people living and working in Challenger Deep.