December 01, 2015

Researchers hope to drill through crust to the Mantle at the crusts thinnest point

In early December, the drill ship JOIDES Resolution will depart Colombo, Sri Lanka, and head for a spot in the southwestern Indian Ocean known as Atlantis Bank. There, it will lower a drill bit and try to screw it through 1.5 kilometres of rock, collecting a core sample as it goes. If all goes well, future expeditions — not yet scheduled or funded — will return and finalize the push into the mantle

Normally, the crust–mantle boundary is thought to be marked by a feature known a.s the Mohorovičić discontinuity, or ‘Moho’, at which seismic waves change velocity. But at Atlantis Bank, the mantle is thought to bubble up as far as 2.5 kilometers above the Moho, making it easier to reach

Beneath continents, the Moho lies 30–60 kilometers down. But beneath oceans it is close enough to be reached with ship-borne drilling equipment. In the drilling campaign — dubbed the Slow Spreading Ridge Moho, or ‘SloMo’ Project — Dick hopes to reach the crust–mantle transition at Atlantis Bank, then one day return with a state-of-the-art Japanese vessel to reach the Moho itself at a depth of 5 kilometers or more

Dick knows that it is possible to reach his preliminary goal of 1.5 kilometres, because he has done it before. In 1997, he led an expedition to Atlantis Bank that got that deep before disaster struck: the pipe snapped off in high winds, corkscrewed down inside the hole and plugged it up. “We’re going to make sure that doesn’t happen this time,” he says.

Along the way, researchers hope to explore not just geology, but biology, too. Geological mapping suggests that seawater may have percolated several kilometres deep at Atlantis Bank, triggering chemical reactions that turn the rock into a type known as serpentinite. These reactions generate methane, a gas that sub-sea-floor microbes often munch for energy. JOIDES Resolution scientists will be checking the rock cores for microorganisms, says Virginia Edgcomb, a microbiologist at Woods Hole who will be on the cruise.




SOURCE- Nature


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