Sub Makes Final Dive To Reach Bottom Of Earth's Deepest Cenote

Scientists this week begin the final leg of a five-year, NASA-funded mission to reach the bottom of Cenote Zacatun in Mexico, the world's deepest known sinkhole. No one has ever reached bottom and at least one diver has died in the attempt. Scientists want to learn more about Cenote Zacatun's physical dimensions, the geothermal vents that feed it and the forms of life that exist in its murky depths. Previous expeditions tested the robotic probe that will make the dive. The Deep Phreatic Thermal Explorer, known as DEPTHX, is a tangerine-shaped submarine designed to survey and explore for life in extreme regions on Earth and potentially in outer space...