A crescent shaped scar on the earth’s crust marks the location of the deepest known part of the world’s ocean. With some areas reaching depths more than 36,000 feet, scientists rely on a range of pioneering deep-sea technologies to survey the unexplored regions of the Mariana Trench. In 1987, the submersible Alvin was the first to visit the nearby Mariana Back-arc, a zone of highly active submarine volcanism and hydrothermal vents hidden 13,000 feet below the ocean’s surface. After returning to the Back-arc 30 years later equipped with the Schmidt Ocean Institute’s new underwater vehicle SuBastian, scientists can now fill gaps in our understanding about the biogeography of these unique ecosystems and to identify possible new species thriving in this extreme deep-ocean environment.