Volume 12 Issue 7, July 2019

Confidence that banded iron formations record oxic conditions during deposition is established, as a model demonstrates that they are formed of primary iron oxides rather than secondarily altered silicate minerals.

Deep soil carbon in tropical catchments can be rapidly mobilized to rivers upon land-use change to agriculture, suggest analyses of dissolved organic carbon. Such carbon stocks had been thought stable for millennia.

Earth’s formation by the accretion of volatile-rich carbonaceous chondrite-like materials, without a need for exotic building blocks or secondary volatile loss, is supported by recognition of a plateau pattern for highly volatile elements.

Ahuna Mons dome on Ceres formed by extrusion of a mixture of brine and solids sourced from a muddy mantle plume, according to numerical modelling of slurry rheology and a gravity anomaly found by the Dawn mission.

Mesosiderite meteorites may originate from a hit-and-run impact on the parent asteroid of eucrite meteorites (probably Vesta), as mesosiderite zircon U–Pb ages are found to coincide with those for eucrites.

Particles from interplanetary dust ablating in Mars’ atmosphere control high-altitude water ice cloud formation, according to numerical simulations of the Martian atmosphere.

The oldest known minerals from Mars have no strong shock features, indicating early cessation of giant impacts there, according to microanalysis of zircon and baddeleyite grains in meteorites.

The Hadley circulation has been weakening over the past 40 years, as simulated by climate models, and not strengthening as found in observation-based reanalyses, suggests an analysis of both methods that points to artefacts in the reanalyses.

Only about 15% of water cycle diagrams include human interaction with water, although human freshwater appropriation amounts to about half of global river discharge, according to an analysis of 464 water cycle diagrams and a synthesis of the global water cycle.

Tropical deforestation induces the loss and transport of old and biolabile soil organic carbon into rivers, suggest analyses of dissolved organic matter in deforested and pristine catchments in the Congo Basin. The mobilized soil carbon is likely to turn into a carbon source.

Soil geochemistry can be more important than climate in controlling carbon storage, its composition as well as stability, but controls are distinct, scale-dependent and variable, according to an analysis of topsoil measurements across Australia.

Biologically available nitrogen in the form of ammonium was abundant in the Late Archaean ocean, according to nitrogen isotope and proxy analyses on 2.7 billion year old shales from Zimbabwe.

Banded iron formations could not have formed by postdepositional oxidation, according to four million hydrogeological box model iterations that failed to reproduce secondary oxidation on reasonable timescales.

Earth’s volatile element composition can be explained without exotic building blocks or late volatile loss, according to matching patterns of volatile element depletion for Earth and carbonaceous chondrites, as revealed by chondrite analyses.

Magma ascent from the near-Moho depth of 24 km to surface eruption took 10 days with melt transport rates of 0.02 to 0.1 m s⁻¹, according to geothermobarometry and diffusion chronometry on primitive olivine crystals from Borgarhraun, Iceland.

Stratification of the Earth’s outer core is regional, not global, and created by lateral heat flux variations at the core–mantle boundary, according to numerical simulations of fluid core dynamics