We have never, ever drilled into the mantle that lies just beneath Earth’s crust. This month, however, scientists are hoping to set the wheels in motion to change all that.
Right now a drilling ship called the JOIDES Resolution (Joint Oceanographic Institutions for Deep Earth Sampling) is on its way to the Atlantis Bank on the South West Indian Ridge of the Indian Ocean. Here, the ship will attempt to drill 1.5 kilometers (0.9 miles) into Earth’s crust in a campaign known as the Slow Spreading Ridge Moho project, or SloMo.
The mission, co-led by Professor Chris Macleod from Cardiff University and Henry Dick from the Woods Hole Oceanographic Institution in Massachusetts, is just the precursor to a much more grandiose task, though. In the 2020s, the team plans to use another drilling ship – the Chikyu – to become the first to ever break into Earth’s mantle.
"We live on this Earth and we ought to know something about what happens beneath us," Walter Munk, an oceanographer at the Scripps Institution of Oceanography in La Jolla, California, told Nature News. Munk led a previous failed expedition to drill into the mantle known as Project Mohole in 1961, while Dick was also part of an ill-fated attempt in 1997, but there are high hopes for this new effort.
The SloMo project is being run by the International Ocean Discovery Program (IODP) as part of Expedition 360 (#exp360), and is heading to this particular region because the mantle is believed to have swelled up beneath the crust, making it more accessible. Usually the mantle is below the Moho, a feature at the crust-mantle boundary, but here it is above, at reachable depths of up to 2.5 kilometers (1.6 miles) – while the Moho may be lower, although still accessible, at about 5 to 5.5 kilometers (3.1 to 3.4 miles) compared to tens of kilometers below land.
In this initial expedition, also known as the Indian Ridge Moho Expedition, the drill from the specialized ship will go only into the crust of Earth and attempt to return a sample. Subsequent expeditions in the coming years, as early as 2018 but with no firm dates yet set, will then attempt to go deeper.
One of the key goals of this expedition will also be to study the levels of serpentinization at these depths, rock created by an active source of heat such as magma from deeper within Earth, which is linked to an abundance of microbes. "If there's far more serpentinite down there, goodness knows how much of it has microbes in it," Professor MacLeod told BBC News.
Image in text above: The SloMo project, courtesy of Nature News
SloMo will run until January 30, and if this initial phase is successful, it could be a crucial step towards the decades-long dream of returning a sample from Earth’s mysterious mantle.
Edit: The Kola Superdeep Borehole went 7.5 miles (12 kilometers) into the ground, but as it was over land it did not break into the mantle. The SloMo project, if successful, will be the first to break into Earth’s mantle.
