The Mohorovičić discontinuity (Moho) is a seismically imaged, first order acoustic interface assumed to represent the transition between the Earth's crust and the underlying mantle in both continental and oceanic settings. To date, this elusive frontier has been a symbolic goal for many geologists, but beyond the reach of available drilling technology. With the recent commissioning of the Chikyu, a new riser-drilling vessel oftheIntegrated Ocean Drilling Program (IODP), the technically challenging goal of drilling to and through the Moho within the ocean basins becomes feasible.