Even amongst the alien worlds of the deep sea, a recently discovered seafloor "hot spring" is an oddball. The 1,300-foot (400-meter) long area, called a hydrothermal vent field, is studded with spindly chimneys that gleam white and cream in the lights of an underwater robot. Clear water rises from underwater geysers in a nearly invisible shimmer, and tiny worms dot the seascape like daisies scattered across a meadow.
"The chimneys have a kind of fairy-castle look to them," says Dave Clague, a marine geologist at the Monterey Bay Aquarium Research Institute (MBARI) in Moss Landing, California. That's because the "snow white" spires are built of calcium carbonate, or limestone, he explains.
But despite the fairytale appearance of it all, these chimneys are wreathed in a scalding plume of water around 500°F (260°C) laden with methane and petroleum-type products that give off a whiff of diesel fuel.
It's a far cry from the more commonly found hydrothermal vents with their rust-colored chimneys that spew charcoal-colored seawater. These "black smokers" are often buried under masses of blood-red tubeworms.
The new field, called the Pescadero Basin vents, holds the Pacific Ocean's deepest known high-temperature vents, about 12,500 feet (3,800 meters) below the surface.
The Pescadero field is also in a strange place to find vents. About 100 miles (150 kilometers) east of La Paz (map), Mexico, the area is covered in sediment, the "mud" of the ocean floor, washed in by the Copper River. "Most hydrothermal vent systems are located on bare, young lava flows with no sediment on them," Clague says.
That mud acts as a filter. Much of the metal in the superheated water—such as iron, zinc, and copper sulfide—gets stuck in the sediment. So the water that emerges from the chimneys is crystal clear.
Black smoker vents disgorge dark gray water because their heavy metals haven't been stripped out. (See pictures of black smokers.)
The high temperatures at Pescadero Basin also cook the organic material in the mud, resulting in those petroleum-like products.
The high heat and noxious water doesn't deter animals like worms or crabs, though. Two-inch-long (five-centimeter) worms—the ones that look like flowers—are "rare elsewhere, but here, there are just swarms of them," Clague says.
Bigger tubeworms, called Riftia, that are usually found along vents like the ones on the East Pacific Rise or the mid-Atlantic Ridge are rare at Pescadero. (Read about how black smokers supercharge evolution.)
In fact, the animal community inhabiting the new vent field seems to be a mix of things found around hydrothermal vents and cold seeps, Clague says. Cold seeps are areas where gases like methane percolate out of the seafloor, but the ecosystem isn't powered by heat.
Methane isn't common in vent fluids, but Clague thinks it's likely that Pescadero's water is chock-full of the compound.
Groping in The Dark
Although MBARI biologists will probably be working on their "alien" haul for years, says Clague, they found the new vents in record time. That's part of what makes the discovery so exciting. Scientists hope to speed up the pace of exploration of the largely unmapped ocean floor.
"Ship time is expensive," Clague says. "If you can knock off 10 days of searching, that's a third of a million dollars depending on how large a ship you're on." So finding a vent field quickly is a big deal.
Historically, researchers had to analyze water samples for chemical signatures and then send a vehicle down in a deep-sea version of the game Marco Polo to get visual confirmation.
Sometimes researchers could be within 33 feet (10 meters) of hydrothermal vents and not even see them, says Donna Blackman, a marine geologist at the University of California, San Diego.
But advances in technology have accelerated the process. Clague and colleagues used a detailed map of the Pescadero Basin to spot features that looked like chimneys and then sent a remotely operated vehicle (ROV) directly to the area.
"I think we've now entered a new era in being able to find these [more easily]," Clague says.
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