Tuesday Afternoon: Finding a Lost City When You Can't Ask For Directions

	Enlarge ImageSitu Studios makes scale models of landscapes you'll never walk on, like this one of the TAG hydrothermal mound at the bottom of the North Atlantic. (photo by Hugh Powell, WHOI)
	Enlarge ImageHow the TAG model might appear on a flyby from a survey robot. (photo by Hugh Powell, WHOI)

Searches for Undersea Vents Bring New Finds

Twenty-eight years after the discovery that hydrothermal vents were spewing superhot water and rare chemicals into the deep ocean, the discoveries are still coming fast. A session on hydrothermal vents this morning -- coincidentally held two-escalators deep under the Marriott Hotel -- focused on new finds in the Arctic Ocean and detailed descriptions of chemistry and sea life around Atlantic vents.

For the self-motivated, Chris German even outlined how to go about finding new vents. (Step one: acquire an undersea robot like the Autonomous Benthic Explorer  [ABE].)

German’s team programmed ABE to traverse a classic zig-zag search pattern (called "mowing the lawn") every 2 km over an area they suspected harbored hydrothermal vents. Sensors on ABE continually sniffed for characteristic temperature or chemistry signals that a vent was near. After the initial broad search, the team refined the search mission, and ABE slowly zeroed in on four new vent areas. The onboard camera took pictures of the sites, revealing billowing clouds of black smoke above rock pillars, with ghostly shrimp swimming around the warm rock.

The search took about 30 days, after which German’s team came ashore and handed over the new locations to Karsten Haase of the University of Kiel, Germany, for a more detailed reconnaissance. His instruments measured the chemistry and temperature of the water and sampled shrimp and mussels to see how similar they were to the creatures clinging to vents elsewhere in the ocean.

The teams named the new sites Red Lion, the Turtle Pits, Wideawake Field, and Lilliput, following a tradition of giving whimsical names to deep-ocean discoveries. Pumping out 396ºC water (nearly four times as hot as water boiling on your kitchen stove), the Red Lion vent was hot enough to singe the protective skin of ABE.

Deb Kelley of the University of Washington described the Lost City hydrothermal vents and presented reasons why further searches might reveal that similar vents, despite their otherworldly looks, are fairly common. After all, along the giant ridges that divide the major ocean basins, seismic thrashing is constantly bringing new rock and volcanic material up to the seafloor.