 Two scientists, J. Corliss and J. van Andel, first witnessed dense chemosynthetic clam beds from the submersible "DSV Alvin" on February 17, 1977, after their unanticipated discovery using a remote camera sled two days before.The Challenger Deep is the deepest surveyed point of all of Earth's oceans; it is located at the southern end of the Mariana Trench near the Mariana Islands group.The depression is named after HMS "Challenger", whose researchers made the first recordings of its depth on 23 March 1875 at station 225.