Before he even got his water samples back to the lab, Dr. Bill Seyfried from the University of Minnesota already knew he had hit gold… It was the same sulphur smell that overpowers you at Old Faithful, Mud Volcano, and other geothermal areas in Yellowstone. As Bill calls it, the “smell of Mother Earth.” But unlike the colorful and bubbling geothermal features that amaze visitors in the park, this odiferous water sample came from 400 feet down at the bottom of Yellowstone Lake. Bill and his team are using some hand-crafted instruments, wielded by the ROV Yogi, to take samples of geothermally-heated water that is bubbling up in the dark depths of the lake. Read the captions to see how his team is making these exciting new discoveries. Photos by Chris Linder, WHOI. Work was completed under an authorized Yellowstone Research Permit.