Drilling into Earth's mantle proposed

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LONDON, March 24 (UPI) -- International scientists say they are preparing to drill off Costa Rica in an attempt to retrieve the deepest rocks ever extracted from beneath the seabed.

The drilling project will initially attempt to reach 1.25 miles under the ocean floor with an ultimate goal of returning even deeper samples from the mantle layer below the Earth's crust, the BBC reported Thursday.

Obtaining rocks from the mantle would provide a geological treasure trove "comparable to the Apollo lunar rocks," the researchers said in an article in the journal Nature.

The mantle accounts for the majority of Earth's volume and mass, stretching from the bottom of the crust down to the Earth's iron-nickel core some 1,800 miles further down.

Much of the mantle is in motion, and the slow churning in this layer plays a key role in the tectonic processes that shape the surface above, the researchers say.

The last attempt to drill into the mantle, Project Mohole, was conducted in 1961 off Baja California. Although it failed, its drill location could be the site of a new effort along with two other potential sites being assessed, including the one being actively investigated off Costa Rica.