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Planetary materials reveal variation in iron isotope composition across planetary bodies. Experiments suggest that this variation can be explained by varying degrees of fractionation during core formation, depending on temperature. The image shows a scanning electron microscope image of an iron isotope exchange experiment: a bright semi-spherical metal which simulates a planets core is found next to a grey, quenched silicate, representing a magma ocean. The black region is the graphite sample container.
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.
The geological record preserves scant evidence for early plate tectonics. Analysis of eclogites — metamorphic rocks formed in subduction zones — in the Trans-Hudson mountain belt suggests modern-style subduction may have operated 1,800 million years ago.
Mineral dust particles interact with solar and terrestrial radiation. Statistical analyses of observational data and global simulations reveal that atmospheric dust is coarser than previously thought, and could cause warming of the atmosphere.
Freezing and thawing of soils leads to large pulses of nitrous oxide release. An empirical model shows that cropland winter nitrous oxide emissions are substantial, calling for a revision of the global nitrous oxide budget.
Variability of iron isotopes among planetary bodies may reflect their accretion or differentiation histories. Experiments suggest nickel may be the ingredient controlling iron isotope signatures, supporting fractionation during core formation.
Over 70% of the volcanism on Earth occurs beneath an ocean veil. Now, robotic- and fibre-optic-based technologies are beginning to reveal this deep environment and identify subaqueous volcanoes as rich sources of sulfur, carbon dioxide and life.
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.
Frictional charging of granular materials may readily occur on Saturn’s moon Titan. Laboratory experiments under Titan-like conditions suggest that the resulting electrostatic forces are strong enough to affect sand transport on Titan.
The moon Phobos is spiralling inwards towards its disintegration to eventually form a ring around Mars from which new moons may form. Simulations suggest that this is just the latest of multiple ring–moon cycles over the history of Mars.
Transient streaks on Martian slopes have been attributed to liquid water. Simulations show that a dry avalanche process involving the flow of gas in the Martian soil due to temperature contrasts can instead explain these recurring features.
The radiative effect of desert dust depends in part on its size. An integrative analysis of observed and modelled dust size and abundance reveals that atmospheric dust is coarser, and less cooling, than previously thought.
Large fluxes of nitrous oxide occur when frozen soils thaw. Field measurements and mathematical models suggest that freeze–thaw events are responsible for 17 to 28% of nitrous oxide emitted from agricultural soils globally.
Grass species vary in their regulation of water use. Remote-sensing data reveal that productivity is more sensitive to atmospheric moisture than precipitation deficits, especially in grasslands where plants loosely regulate water use.
Most monitoring of methane well leakage focuses on emissions of methane gas to the atmosphere. In a controlled-release field experiment, significant methane also persisted in aquifer groundwater due to lateral migration along bedding planes.
Atmospheric CO2 levels varied across glacial–interglacial cycles. An analysis of ice-core CO2 identifies a lower limit to glacial CO2 concentrations, which may reflect a negative biosphere feedback to decreasing CO2 levels.
Magma movement is thought to trigger volcanic tremor. However, analysis of seismic data suggests that tremor prior to the Bárðarbunga eruption in Iceland instead marked the crust cracking open, whereas subsequent magma flow was seismically silent.
The timing of onset of modern-style plate tectonics on Earth is unclear. Identification of eclogite rocks—typically formed during subduction—in the Trans-Hudson orogen implies modern-style tectonics may have been active 1,830 million years ago.
The crystal structure of iron under the extreme pressures and temperatures of Earth’s core is debated. Numerical simulations suggest that the body-centred cubic structure of iron is stable under inner-core conditions.
Planetary materials reveal variation in iron isotope composition across planetary bodies. Experiments suggest that this variation can be explained by varying degrees of fractionation during core formation, depending on temperature.