Sounding the deepest spot on Earth

Challenger Deep in the Mariana Trench near Guam is the deepest spot on Earth. How do we know? We didn't look for it. We listened.

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National Geographic Explorer-in-Residence and Filmmaker James Cameron has announced he will soon operate a one-man submarine 7 miles deep to the Pacific's Mariana Trench, the deepest point on earth. Cameron plans to spend as much as 6 hours on the ocean floor and will film and take specimens for scientific study.