Today we took our last sediment samples, saw our last shrimp and bid farewell to the Edmond Vent Field. Tonight we pointed our bow west towards Mauritius. In just over two days we will arrive at Port Louis, where we began this expedition 30 days ago.

One of the main goals of today’s final Jason dive was to collect core samples for Microbiologists Anna-Louise Reysenbach and Dorothee Gotz and Geochemist Darryl Green. By collecting cores, they can see the “history” of microbial life at this vent field in the various sediment layers, and determine what bacteria live in each layer. For example, bacteria deeper in the sediment may thrive in a higher temperature environment.

Measuring the temperature of the sediment with the ICL Temperature-probe, the scientists discovered that just below the surface the mud is hot, up to 212°F (100°C) in places. Then, using a large clear tube, Chief Pilot Will Sellers directed Jason’s manipulator to plunge the tube into the side of an orange-colored slope where curling wisps of hot hydrothermal fluids were visible.

After capturing a load of sediment in the tube, he quickly returned it to Jason’s basket for the microbiologists.

With the rusty-looking sediment now in hand, Anna-Louise and Dorothee will analyze the core samples for bacteria. “We want to take stock of the bacteria living there before we can start answering questions like, what are these bacteria doing in this environment? How do they change the chemistry of the environment? Which bacteria are dominant?” said Dorothee.

In celebration of our last day on station of this expedition, Steward Mirth Miller prepared a 28-pound turkey with all the usual trimmings, including squash and cranberry pecan pie. Before eating we gathered on Knorr’s bow for a sunset toast honoring the late MIT Geochemist John Edmond, a hydrothermal vent research pioneer who died earlier this month in Massachusetts. We named this site for John after we discovered it last week.

“John, here we are at sea again where we first met you and where we say good bye,” read Chemist Bob Collier from a note. Then he tucked the paper into an empty bottle, sealed it, and at the end of the ceremony, Bob lifted his arm and tossed the bottle into the waves.

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