Not since the drilling of the Russia’s Kola Borehole have scientists ventured this deep.
Japanese scientists have announced a plan to drill through the Earth’s crust and reach the mantle. The major initiative would be a first for humankind. Despite multiple previous attempts and multiple boreholes of significant depth, we’ve never managed to drill far enough to see what lies beneath the Earth’s rocky crust. Instead, our knowledge of the mantle is mostly based on indirect observations, like the speed at which seismic waves propagate through the planet’s internal geometry.