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Ancient hydrothermal deposits formed in the Martian subsurface may be the best targets for finding evidence for ancient life on Mars, and clues about the origin of life on Earth.
Recurring slope lineae are likely to be dry granular flows with little-to-no requirement for large volumes of liquid water on Mars, according to an emerging view that is supported by topographic analyses.
Continental rifts are stores and sources of abundant carbon, according to calculations of carbon storage, enrichments and mobilization in rift systems. Continental rift systems are likely to play an important role in Earth’s deep carbon cycle.
Storm-resolving simulations of the tropical Atlantic region bring out the doldrums, a zone of calm and variable winds in the deep tropics that was described in the nineteenth century and then forgotten.
Many of the world's saline lakes have been shrinking due to consumptive water use. The Great Salt Lake, USA, provides an example for how the health of and ecosystem services provided by saline lakes can be sustained.
Enhanced protection is needed for freshwater bodies in the United States — in particular impermanent streams and wetlands outside floodplains — according to an assessment of their value and vulnerability.
The careful compilation and interpretation of molybdenum isotopes can track the expansion of sulfidic bottom waters. A synthesis and analysis of data from two Mesozoic ocean anoxic events and the Palaeocene-Eocene thermal maximum applies these techniques to constrain past ocean deoxygenation.
The Sustainable Development Goals map out a broad spectrum of objectives. Analytical tools in form of the Index and Dashboards provide a starting point to set national baselines, and allow comparison of the SDGs with other indices of well-being.
The only temperature profile of the lowermost Venusian atmosphere appears unstable. Compositional heterogeneity due to density-driven separation of N2 from CO2 gas in the lower atmosphere of Venus may be a viable explanation.
Dehydration of subducting slabs could create a reservoir of water in the overlying mantle. A synthesis of thermal model results, however, shows that slab dehydration is slow over geological time scales, so such reservoirs are probably rare.
The atmosphere can hold more water in a warming climate, which may lead to more extreme rainfall events. An analysis suggests that links ofrainfall extremes with daily temperature variations do not provide a reliable basis for projections.
External metal inputs to oceans affect ocean productivity and metal cycling. A synthesis of researchreveals that internal processes such as metal retention, recycling and remineralizationare also important.
The net carbon flux on land comprises emissions from land-use change and uptake by vegetation. An evaluation of vegetation models suggests that emissions from land-use change, and thus the terrestrial sink, may be substantially underestimated.