Tuesday, April 28, 2015

Hot water!

Last night Jason successfully landed at the ABE hydrothermal vent field, at a depth of about 2140m. Jason touched down directly next to a pair of smaller spires, glimmering white with sulfur and microbes. Shimmering water rose from the tops of the chimneys, where shrimp and a particularily feisty crab had made its dwelling. Several other towers loomed out of the black as Jason's lights touched their bases.
Hydrothermal vents occur primarily in areas where magma is close to the surface such as around tectonic plate boundaries. Seawater sinks into the crust through fractures and pore spaces where it comes close to the magma below and becomes superheated and buoyant. This heated water then moves back through the crust and is expelled as hydrothermal fluid. Vent chimneys are formed when the metals in the superheated fluid precipitate as they are ejected from the subsurface and mix with cold seawater. Initially the minerals are amorphous, and the structures that form are soft and friable, often referred to as "beehives".
"Beehive" chimney from 2140 m in the ABE vent fields

With time, iron, copper and zinc minerals -pyrite, chalcopyrite and sphalerite, become crystalline and harden, making large structures like we saw today. Heat-loving (thermophiles) microbes colonize these structures and then very quickly other invertebrates appear in places that are not too hot (more soon on the microbes and biology of the vents).

Today we collected numerous chimney samples to explore the microbes associated with these rocks. We also took temperature measurements and samples of the hydrothermal fluids being emitted from the chimney structures. To do this, we use an Isobaric Gas-Tight (IGT) sampler that is designed specifically to fill slowly and maintain the fluid samples at seafloor pressure (which is more than 200 times atmospheric pressure. Just think what that would do to a styrofoam cup if you took it down that deep! We'll do that experiment, and show you the result in an upcoming post).
IGT sampling fluid of about 280 degrees Celsius

After 8 IGT samplers-full, several sulfides and more, we are all ready for bed. Tomorrow. we'll give you a glimpse into some of our ABE scientific treasures.

Contributed by Morgan Haldeman

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