In the western Pacific Ocean lies the Izu-Bonin-Mariana (IBM) arc-trench system, created from the subduction of the Pacific plate which began some 51 million years ago and continues today.  The IBM is home to the deepest known point in the ocean - the Mariana Trench, which in its famous Challenger Deep, reaches a known depth of 10,994 meters (± 40 meters).  Early explorations of the Trench focused on determining its depth.  When on 23 January 1960 Swiss engineer Jacques Piccard and US Navy submariner Captain Don Walsh took the first manned vessel – the bathyscaphe Trieste, down the Challenger Deep to 10,911 metres (35,797 feet), they were uncertain whether they would make it back to the surface.  Make it back they did, and what they saw down in the Deep surprised and delighted all….

“The bottom appeared light and clear, a waste of snuff-colored ooze. We were landing on a nice, flat bottom of firm diatomaceous ooze…. as we were settling this final fathom, I saw a wonderful thing. Lying on the bottom just beneath us was some type of flatfish, resembling a sole, about 1 foot long and 6 inches across. Even as I saw him, his two round eyes on top of his head spied us - a monster of steel - invading his silent realm. Eyes? Why should he have eyes? Merely to see phosphorescence? … Slowly, extremely slowly, this flatfish swam away. Moving along the bottom, partly in the ooze and partly in the water, he disappeared into his night.” ~ Jacques Piccard, Seven Miles Down: The Story of the Bathyscaph Trieste (1961).

Since Piccard and Walsh’s descent, only one other person has been to the bottom of the Challenger Deep.  On 26 March 2012, in his much more advanced deep-sea submersible the Deepsea Challenger, James Cameron reached the bottom at a depth of 10,908 metres (35,787 feet) and remained there for some 3 hours before ascending, bringing with him HD video of this rarely viewed environment.  Thanks to the advancement of robotics, exploration of the Mariana Trench does not rely solely on manned missions.  Remotely Operated Vehicles (ROVs) have provided us with images, video footage, and even samples brought from the deep.  Notwithstanding the difficulties in deep-sea exploration, at 2,550 kilometres (1,580 miles) long, and an average width of 69 km (43 miles), studying the Trench is no small feat.  But with every trip we have learned more about this unique and extraordinary environment and its inhabitants.

This story was written for The Marine Professional, a publication of the Institute of Marine Engineering, Science & Technology (IMarEST).