Kris Walz writes: Today is Earth Day, a perfect day to be afloat on the surface of the ocean, exploring the deep-sea communities thousands of meters below. Over 70 percent of Earth’s surface is covered by oceans making the seafloor one of the world’s largest habitats. Covering roughly 360 square kilometers (140 million square miles), the ocean contains about 95 percent of all the available living space on Earth, and yet, only five percent of the ocean has been observed by human eyes. Millions of species have yet to be described and many new communities and systems discovered. Scientists have their work cut out for them!

The ROV Doc Ricketts has made 754 dives to date and with each dive we explore thousands of meters of seafloor or pelagic waters (MBARI’s ROV Ventana has made nearly 4,000 dives and our retired ROV Tiburon made over 1,000 dives). We study the ocean for many reasons. Perhaps the most important reason is to determine how human activities affect ocean warming, acidification, and expanding oxygen minimum zones.

On today’s dive, we continued our exploration of vent communities on the Alarcón Rise, north of the area we explored yesterday. We examined three chimney systems. One of the most interesting moments was when Verena Tunnicliffe aimed the ROV camera at a dense cluster of Alvinella tube worms atop a chimney, to observe the animals for about 30 minutes. I remember my professor, Todd Newberry at the Univeristy of California, Santa Cruz, encouraging his students to stop and really look at the organism, ask them the questions, and watch for answers. “The animal is always right,” he would tell us. Today we did just that with ROV Doc Ricketts, and everyone (pilots, scientists, and crew members on the bridge) asked questions and watched patiently for answers.

We noticed behaviors not described before and interesting interactions between worms of the same species and other vent animals. Scientists would not be able to make these observations without the aid of an ROV and high-definition video. Viewing these habitats with the human eye is invaluable for making discoveries, sometimes reinforcing what we thought these animals might do after analyzing their morphology, and sometimes proving us wrong.

The last chimney system of the day provided the most spectacular vent images for everyone on board. Again, we were glued to the monitors displaying ROV video from 2,300 meters below us. The 16-meter chimney had a large flange near the top, a five-foot horizontal projection from the vent. Beneath the flange, we could see shimmering water where the hot venting fluid pooled above the cold seawater (also described during Leg 5).

Shana Goffredi writes: Today I saw the most beautiful and mesmerizing thing that I’ve ever seen in nature. Under one volcano, there was a large flange with an upside-down reflecting pool of hot water. Tube-dwelling alvinellid polychaete worms lived all around the rim. We named it Glitter Lake because of glittery pyrite (otherwise known as fool’s gold), lining not only the worm tubes, but also the “bottom” of an upside down “lake” that measured about 1.5 meters in diameter. Still photographs cannot do it justice. Video was really the only way to capture the swirling eerie mist at the surface of the upside down lake. We decided that the alvinellid worms should be the new face of deep-sea biology. They are simply adorable, yet, they are extreme in their affinity towards hot venting fluids. They often extend their long fuzzy bacteria-covered bodies into nearby tubes to explore, bite, or perhaps court their neighbors and then they disappear into their tubes just as quickly—all the while resembling little squirmy jack-in-the-box toys.

We spent nearly an hour observing this incredible feature. We noticed in one area that the alvinellid worms hang their fuzzy rear ends out of their tubes, perhaps nourishing their bacterial fur coats with the toxic sulfides in the hot vent water. These bacteria use hydrogen sulfide, instead of light, for both energy and electrons to drive the conversion of inorganic carbon dioxide into organic carbon. The worms are thought to eat these bacteria for nutrition and, as with all of the animals in these venting habitats, rely nearly exclusively on geochemical energy from the Earth, as opposed to the sun. We are likely the only people ever to see this truly spectacular scene on the remote seafloor. There are sure to be so many more like it that defy imagination about what actually lives on this planet.