Fifty years ago, man reached the bottom of the Mariana Trench On January 23, 1960, Swiss oceanographer and engineer Jacques Piccard and US Navy Lieutenant Don Walsh on the bathyscaphe Trieste sank to the bottom of the Challenger Abyss, located in the deepest sea trench on the planet - Mariana. Sensors on board recorded a depth of 11,521 meters, but more accurate measurements taken a third of a century later reduced it by 600 m.