Due to the radiative thermal conductivity of the mineral olivine, only oceanic plates over 60 million years old and subducting at more than 10 centimeters per year remain sufficiently cold to transport water into Earth's deep mantle. This was found by scientists from the University of Potsdam and from the Helmholtz Center for Geosciences (GFZ) Potsdam, together with international colleagues, by measuring the transparency of olivine under conditions in Earth's mantle for the first time. Their results are published in the journal Nature Communications.