Deep drilling project digs into Earth’s structure and past

An international marine research program, known as the Integrated Ocean Drilling Program (IODP), is planning to drill down almost 10 kilometres below the ocean floor in an attempt to reach the Earth's mantle. The goal is to bring back uncontaminated samples of mantle rock for study, which should help to give us a better understanding of Earth's structure and formation.

Although we know a lot about the interior of the planet, none of what we know is from direct study of the layers below the crust. We know what we do by studying four different things: how vibrations from earthquakes pass through the planet, the rotation and inertia of the Earth, the study of the Earth's magnetic field and laboratory experiments that tested some of the processes that were thought to be going on in both the mantle and core.

Previous attempts have been made to drill down to the mantle.

Project Mohole was a U.S.-led effort in the 1960s that tried to reach the Mohorovičić discontinuity, which is the boundary between the Earth's crust and the mantle (named for the seismologist that discovered it). The attempt only drilled down to 183 m below the ocean floor — off the coast of the Guadalupe Island, Mexico — before the U.S. Congress canceled the project for being too expensive.

The Kola Superdeep Borehole (KTB) was a Russian project that ran for 35 years, from 1970 to 2005, before being shut down by the Russian government, also for being too expensive. The project still holds the world record for deepest hole ever drilled and deepest artificial point on Earth, which it set in 1989. Two other projects surpassed it as 'deepest bore hole', first in 2009 and then in 2011. The KTB project found some surprising results in its attempt, including that the rocks in the Mohorovičić discontinuity, which they expected to show a transition between granite and basalt rock, are actually fractured and saturated with water, and the discovery of mud flowing to the surface of the hole that was saturated with hydrogen gas.

The IODP's mission to reach the mantle is being run from the Japanese ship Chikyū, which has already set a new record for deepest scientific ocean drilling, reaching 2,466 m below the ocean floor on September 9th. If the IODP succeeds, likely in 2020, it will bring back the first uncontaminated samples of mantle rock, something that has been long sought after by scientists. The closest so far has been samples from volcanoes, but those are either contaminated by sea water or by magma from closer to the surface.

Canada has been involved in ocean drilling projects since 1995, when it joined the Ocean Drilling Program, and has been a member of the IODP since 2004.

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