Scientists speculate that the silicates stuck to the mantle might also be caught up in mantle convection and carried to the surface, accounting for reports of core material in lava erupting from hot, spot plumes, like those under Hawaii.
The billionaires are bankrolling expeditions to reach the deepest place in the ocean, a spot called the Challenger Deep that lies at the bottom of the Mariana Trench, seven miles below the surface of the South Pacific.