Starting this week, scientists will begin a multiyear expedition to drill below the Earth’s crust, reports Nature. The quest to reach the Earth’s mantle began more than 60 years ago when Scripps Oceanographer Walter Munk conceived of the idea while talking with his colleagues over drinks in 1957. The scientists began work on Project Mohole, which had the goal of reaching the crust-mantle transitional area known as the Mohorovičić discontinuity or the Moho Layer. First identified in 1909, the Moho is a boundary layer that separates both the oceanic crust and continental crust from the underlying mantle. The early explorers began drilling in 1960 off the coast of Mexico, but they had to stop after only 183 meters due to cost overruns that killed the project.
Despite this setback, Project Mohole kicked off a series of similar ocean drilling projects that have greatly expanded our knowledge of Earth science, including important discoveries about plate tectonics and subterraneous microbial life. Now in 2015, another group is poised to pick up where others have left off. These deep rock areas are an unexplored frontier and the study of these underground treasures “is one of the great scientific endeavors of the century”, said Henry Dick, a Woods Hole geophysicist and co-leader of the 2015 expedition.
The researchers have selected a drilling location in the Atlantis Bank, which is situated in the southwestern Indian Ocean. Due to its unique geology, the ocean is relatively shallow in this area and the mantle rises close to the surface, making it easier to access. It also means there are less hard-to-crack crustal rocks, which have thwarted previous attempts to access this part of the Earth’s crust. Initially, the group plans to use the JOIDES Resolution drill ship to drill down 1.5 kilometers into the crust, collecting a core sample as it moves through the layers of rock. If this first mission proceeds smoothly, then the team will seek funding for additional missions to break into the mantle, first drilling down 3 kilometers in Phase 2 and then gradually more than 5 kilometers in Phase 3.
Besides reaching the mantle, the team of researchers also are interested in studying the geology and biology of the area. Recent studies suggest the Atlantis Bank may be a source of serpentinite rock, which forms when seawater reacts with peridotite in the mantle rock, especially those that have been moved upwards by plate tectonics. They also hope to find microbial species that live off methane, which is produced when this serpentinite rock is formed. The first phase of this research will begin this month and will last until January 30, 2016. The second and third phase will begin at an undetermined date in the future using the Japanese drill ship Chikyu, which is capable of drilling down the 6 kilometers need to reach the Moho layer.
