Abstract
Ocean drilling project has historically been commenced by Project MoHole in 1961drilling into mantle through the Mohorovicic discontinuity at 6km below seafloor at the same timing of the Apollo project sending human to the Moon. It has been more than 50 years since then, and it has been just 50 years since the launch of Deep Sea Drilling Project (DSDP) in 1968 after Project MoHole. A compilation of holes into the ocean crust cored by scientific ocean drilling since the beginning of DSDP to 2018 highlights that only 38 holes deeper than 100m have been cored in oceanic crust and the total recovered ocean crustal material represents <2% of the cores. However, despite this relative paucity of material, scientific ocean drilling has provided essential and hitherto unavailable observations for advancing our understanding of the processes that repave nearly 70% of Earth's surface over short geological time scales (<200 million years) : these include better knowledge of ocean crust architecture and the accretion in processes in the axial zone of mid-ocean ridge spreading centers. It is still our ambition to explore the deep interior of our planet by scientific drilling in ocean, the most successful, long-term international scientific collaboration in any field. The Mohole-to-Mantle (M2M) project will sample for the first time upper mantle peridotites at a fast-spreading mid-ocean ridge. This will be achieved by drilling by D⁄V Chikyu through intact fast-spread oceanic crust, and ∼500m into the mantle lithosphere.
