The human-occupied vehicle (HOV) Alvin at the surface after a dive, during its recent science verification expedition at locations on the Puerto Rico Trench and Mid-Cayman Rise in the Atlantic. The world’s most productive sub was recently certified to dive to a maximum depth of 6,500 meters (4 miles). The new maximum depth puts roughly 99% of the global seafloor in reach—including the lower Abyssal Zone and the upper Hadal Zone, home to ultra-high-temperature hydrothermal vents, newly discovered volcanic processes, untold mineral resources, and much more. This will also give the science community an unprecedented opportunity to visit a critically under-studied part of the planet that plays a role in carbon and nutrient cycling and that will offer a view into how life might be evolved to conditions in oceans beyond Earth.