On March 5, oceanographers mourned the passing of a cherished colleague: an undersea robot affectionately known as ABE (short for Autonomous Benthic Explorer).

ABE may not have had the renown of DSV Alvin, its illustrious forebear, or the gee whiz technology of its modern contemporaries, but it was a pioneer of underwater robotics. During its fruitful 16-year career the autonomous bot made more than 200 deep dives, navigating the treacherous terrain of the sea floor and mapping underwater mountain chains with little input from above. ABE was ultimately lost at sea off southern Chile during a research dive.

As humans have set out to examine the deepest, most mysterious ocean depths, ABE and his ilk have been indispensable workers. Click through the gallery for the greatest discoveries made by mechanical deep-sea explorers.