In an unprecedented $1 billion mission to reach the Earth's mantle, geologists are set to start drilling 3.7 miles (6 km) beneath the seafloor, to reach the Earth's mantle. And according to project co-leader Damon Teagle, "It will be the equivalent of dangling a steel string the width of a human hair in the deep end of a swimming pool and inserting it into a thimble 1/10 mm wide."
For sure — it's not going to be easy. The mantle is a 1,860 mile-thick layer of slowly morphing rock between the Earth's crust and the core. And to get there, geologists will have to slowly and patiently make their way through ultra-hard rocks with drill pipes that are 6.2 miles in length. And given that each drill bit lasts for about 50 to 60 hours, the entire project could take years.
Speaking to CNN, Teagle referred to it as "the most challenging endaevor in the history of Earth science." And to make all the more difficult, the geologists are hoping to bring up some samples.
Teagle recently did an NPR radio interview where explained the purpose of the mission:
[If] we really want to understand how our Earth has evolved over its history since its formation, then we need to have a very precise view of the chemical composition of the mantle...
[We] are interested in the formation and evolution of the ocean crust, and also about the nature of the mole hole — which is this boundary between the crust and the mantle and the mantle itself — [so] we're drilling into very hard, crystalline rocks — rocks that formed from the crystallization of magma. Whereas the oil companies, when they're drilling, they're drilling into sedimentary rocks that have been laid down in the oceans over the eons and captured organic material that eventually evolved to form petroleum and gas.
So actually, the rocks we're drilling into are the rocks that sit beneath the sedimentary reservoirs that host the oil and gas. So they can drill deeper holes — but they're not drilling into such hard rocks.
To get a head start on the drilling, the geologists are using a Japanese deep-sea drilling vessel called Chikyu that's capable of carrying 10 km of drilling pipes. The boat already holds the world-record for the deepest hole in scientific ocean drilling history, over 1.3 miles (2.2 km) into the sea floor.
This is not the first attempt to reach the mantle. Back in 1962, a group of Soviet geologists launched Project Mole Hole, but never made it all the way.