Japan's Chikyu vessel should be up to the task This spring, scientists will try to retrieve the deepest types of rock ever extracted from beneath the seabed.
The drilling project is taking place off Costa Rica, and will attempt to reach some 2km under the ocean floor.
Writing in the journal Nature, the co-chief scientists say their ultimate goal is to return even deeper samples - from the mantle layer below the crust.
Obtaining these rocks would provide a geological treasure trove "comparable to the Apollo lunar rocks" they write.
One of the co-chiefs, Damon Teagle from the University of Southampton, UK, told BBC News: "There are some fundamental questions about the way that the Earth has evolved over its history that we will only be able to answer once we completely understand the structure of the crust overlying the mantle, the interface between the mantle and the crust (known as the Mohorovicic Discontinuity, or Moho), and then also the nature of the mantle itself."
The mantle makes up the bulk of our planet's volume and mass. It stretches from the bottom of the crust down to the Earth's iron-nickel core some 2,900km further down.
Its rocks are distinct in composition from those that make up the continents and the ocean floor.
They are thought predominantly to be peridotites, which comprise magnesium-rich, silicon-poor minerals such as olivine and pyroxene.
The properties of these rocks and the conditions to which they are subjected mean much of the mantle is in motion.
Slow convection in this dominant layer plays a key role in the tectonic processes that help shape the surface above.
Scientists already have a range of samples from deep inside the Earth. Some of these were lifted up in the processes that built Earth's mountain ranges, and others have come up in the lavas of volcanoes.
But all the samples are altered in some way by the means that brought them to the surface, and scientists would dearly love to see pristine specimens.
"We need to know the exact chemical composition, and this composition varies from place to place," said Benoit Ildefonse from the Montpellier University 2, France.
"It's important because, depending on the composition, the physical properties of the mantle will also vary and eventually will have some effect on the dynamics of the Earth - on the way this mantle is able to move, on the way it's able to eventually partially melt and produce some magma that is carried out to the surface, creating the new ocean crust."
The last attempt to drill into the mantle, Project Mohole, was conducted in 1961. It failed, but its drill location could be the site of a new effort. Two other potential sites are being assessed, including one being actively investigated this spring Drilling into the mantle on land is impractical because the continents are where the crust is thickest - some 30-60k
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