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Earth’s mantle has cooled since the Archaean. Geochemical identification of anomalously hot lavas formed above the Galapagos Plume 89 million years ago, however, implies that a hot mantle reservoir may have persisted for billions of years.
The influence of tectonics, continental weathering, and seafloor weathering in the geological carbon cycle remain unclear. Here, the authors develop a new carbon cycle model and, through comparison with proxy data, critically evaluate the influence of these components on carbon fluxes since 100 Ma.
The composition of the early Earth’s atmosphere remains unclear. Here, the authors using fluid inclusions trapped within quartz crystals show that at 3.3 Ga the atmosphere had a lower 129Xe excess than today, and suggest that comets may have brought xenon to the Earth’s atmosphere during terrestrial accretion.
The damming of rivers has large impacts on the balance of riverine carbon (C) processes and fluxes to the oceans. Here, the authors use decadal riverine organic C loads and model C transformations to quantify in-reservoir organic C burial, mineralization and assess decreases in riverine exports to the oceans.
The long-term cooling of Earth's mantle is recorded in the declining temperature and volume of its volcanic outpourings over time. However, analyses of 89-million-year-old lavas from Costa Rica suggest that extremely hot mantle still lurks below.
The composition of Earth's oldest crust is uncertain. Comparison of the most ancient mineral grains with more recent analogues suggests that formation of the earliest crust was heavily influenced by re-melting of igneous basement rocks.
Hidden under many kilometres of silicate mantle material, the cores of Earth and other planets are hard to investigate. The Psyche spacecraft, designed to visit a metal body that may be a core stripped of its mantle, could bring a close-up view.
There are many unanswered questions regarding how the biomolecules and biomechanical processes that define life came to be. A collection of Articles in this issue show how intermediates in RNA synthesis might have formed and how the initiation and evolution of RNA replication might have occurred.
Hints from seismic tomography and geochemistry indicate that Earth's mantle is heterogeneous at large scale. Numerical simulations of mantle convection show that, if it started enriched in silicates, the lower mantle may remain unmixed today.