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Purported 3,465-million-year-old microfossils from Australia have been the subject of considerable debate. A method to distinguish between pristine fossils, mineral artefacts and subsequent microbial contamination will aid the search for ancient biogenic material.
The fate of sinking particulate organic matter in the world ocean is a key source of uncertainty in the global carbon cycle. Model simulations suggest that atmospheric carbon dioxide concentrations depend critically on the depths that these particles typically reach.
Titan's surface is covered by vast fields of linear dunes, probably composed of organic sand-sized particles. The study of linear dunes in China suggests that sediment cohesiveness can be as important as wind direction in the creation of these dune forms.
The Pacific and Australian plates collide and interact in complex ways around New Zealand. Electrical resistivity data reveal that subduction-zone fluids exert an important influence on deformation in the region.
The Salton Sea is located in a sedimentary basin at the southern termination of the San Andreas fault. High-resolution seismic data indicate that the basin formed and grew by active subsidence at its southern end.
Modern terrestrial microbes have shown a puzzling ability to use reduced forms of phosphorus not commonly found on Earth. An examination of glasses formed in the ground by lightning suggests that lightning strikes can generate these phosphorus species.
Fossils from southern China provide evidence for a mass extinction during middle Permian time, 260 million years ago. The close association of this event with an outpouring of lava, initially into the sea, indicates that explosive volcanism may have been the cause.
Global warming 55 million years ago was accompanied by a massive injection of carbon into the ocean-atmosphere system, but the resulting climatic warming was much greater than expected from the modelled rise in atmospheric carbon dioxide alone.
It is unclear whether the modern processes of mercury cycling — such as mercury deposition in polar regions — operated before anthropogenic emissions. Ice-core records from Antarctica now reveal strikingly high mercury concentrations during the coldest glacial periods.
Seafloor vents spewing mineral-rich plumes of hydrothermal fluid — termed black smokers — can persist at mid-ocean ridges for decades or longer. Earthquake data indicate that ongoing magma injection may determine their locations.
Some components of the climate system continue to adjust long after atmospheric greenhouse-gas levels have stopped changing. A coupled climate–vegetation model shows that forests can be committed to die-back or expansion before change is observed.
Understanding millennial-scale climate variability provides context for present and future climate change. It now emerges that temperatures were spatially and seasonally more heterogeneous over the past 1,000 years than previously thought.
Large and rapid global sea-level changes indicate that polar ice sheets may have ephemerally existed during the Cretaceous greenhouse climate. Two oxygen isotopic studies provide evidence for and against this conclusion.
Ammonia is a significant atmospheric pollutant whose global distribution is poorly understood. Satellite measurements highlight ammonia hotspots across the globe and indicate that current inventories may underestimate emissions in the Northern Hemisphere.
