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Challenger Deep

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Adventure stories are just the lead up to great science. In anticipation of this, the National Geographic sponsored and broke the story of the second descent to the deepest part of the world’s oceans:

Sea cucumber: enypniastes

At noon, local time (10 p.m. ET), James Cameron’s “vertical torpedo” sub broke the surface of the western Pacific, carrying the National Geographic explorer and filmmaker back from the Mariana Trench’s Challenger Deep—Earth’s deepest, and perhaps most alien, realm.

The first human to reach the 6.8-mile-deep (11-kilometer-deep) undersea valley solo, Cameron arrived at the bottom with the tech to collect scientific data, specimens, and visions unthinkable in 1960, when the only other manned Challenger Deep dive took place, according to members of the National Geographic expedition.

After a faster-than-expected, roughly 70-minute ascent, Cameron’s sub, bobbing in the open ocean, was spotted by helicopter and would soon be plucked from the Pacific by a research ship’s crane. Earlier, the descent to Challenger Deep had taken 2 hours and 36 minutes.

Before surfacing about 300 miles (500 kilometers) southwest of Guam, Cameron spent hours hovering over Challenger Deep’s desert-like seafloor and gliding along its cliff walls, the whole time collecting samples and video.

Retired U.S. Navy Capt. Don Walsh, who descended to Challenger Deep in 1960, said he was pleased to hear that Cameron had reached the underwater valley safely.

“That was a grand moment, to welcome him to the club,” Walsh, said in a telephone interview from the sub-support ship.

“There’re only three of us in it, and one of them—late Swiss engineer Jacques Piccard—”is dead. Now it’s just Jim and myself.”

After breaching the ocean surface, the DEEPSEA CHALLENGER was first spotted by a helicopter owned by Microsoft co-founder Paul Allen, who longtime Cameron friend. Allen was on the scene for the historic dive and posted live updates of the event on Twitter from aboard his yacht, the Octopus, which is providing backup support for the mission.

The grand pictures and the as-yet-unimagined biology will come later. In the meanwhile, MSNBC hangs a lovely story on plate tectonics on the hook of this adventure story:

Earth's tectonic plates

Yet some scientists are trying to delve deeper still, albeit by means of technology very different from Mr. Cameron’s magnificent machine. They are trying to look at the geological makeup of the Earth’s insides deep beneath the Mariana Trench in search of a few pieces to an epic puzzle: How does water move from the Earth’s crust to its interior?

Research indicates that water is what allows the Earth’s mantle, a colossal layer as rigid as steel, to stay viscous. And scientists know that water comes out of volcanoes — a conduit for material to the surface world from the Earth’s innards — another telltale sign there’s water in the mantle. It’s just not clear how it’s getting all the way down there.

The Mariana Trench provides a great venue to test such a question. It’s a subduction zone, the boundary of two tectonic plates, where one plate is slowly diving beneath the other.

“The Pacific Plate is bending and plunging down into the Earth, and as it bends it cracks,” Lizarralde told OurAmazingPlanet.

Some scientists hypothesize that if those cracks extend between 4 and 6 miles (6 and 10 km), deep enough to reach the mantle, they could be the conduit for water to reach the Earth’s interior, said Doug Wiens, a professor of earth and planetary science at Washington University in St. Louis.

If they see evidence of a particular mineral called serpentinite — a mineral created when water reacts with another mineral commonly found deep in the Earth — the team may have tracked down the delivery system that injects water into the mantle.

Water can’t simply hitch a ride to the Earth’s interior aboard any ordinary rock. If the rock is too flimsy, the crushing pressure and heat in the Earths’ crust will essentially squeeze out all the water before it gets anywhere near the mantle. But serpentinite’s crystal structure provides a kind of hard, mineral suitcase for water molecules, allowing them to pass through the heat and pressure of the crust, and reach the mantle unscathed.

When all the data have come in, by early 2013, the scientists say they will eventually be able to map a good part of the geological makeup beneath the Mariana Trench to a depth of about 60 miles (100 km).

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Written by Arhopala Bazaloides

March 26, 2012 at 4:12 am

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