A deeper dive into Earth's mantle: A coherent section of drilled rocks provides a mineralogical glimpse of the oceanic mantle

Examining the composition and dynamics of Earth’s upper mantle—the largest layer of Earth’s interior—can reveal its biogeochemical effects on the marine system. However, it is situated 6 to 70 km below Earth’s surface and is challenging to study. Along the Mid-Atlantic Ridge in the North Atlantic, tectonic activities move mantle rocks closer to the ocean floor in a region called the Atlantis Massif. Although it is relatively easy to obtain samples from this area, it still requires drilling kilometer-deep holes in the ocean floor. On page 623 of this issue, Lissenberg et al. (1) report the recovery of a 1268-m-long section mainly composed of peridotites—the primary rock of Earth’s upper mantle—at the Atlantis Massif. The depth far exceeds those recorded in previous drilling efforts (2) and creates opportunities to discern structural and mineralogical features of the mantle and how it interacts with the hydro- and biospheres.