Articles in 2015

Mercury’s surface is darker than expected given its low iron content. The delivery of cometary carbon to Mercury in micrometeorite impacts may explain the planet’s globally low reflectance.

Forests may be vulnerable to future droughts. A tree mortality threshold based on plant hydraulics suggests that increased drought may trigger widespread dieback in the southwestern United States by mid-century.

Subducting oceanic crust is sometimes observed to stagnate in the lower mantle. Laboratory experiments show that high pressures in the deep Earth may strengthen mantle rocks, increasing their viscosity and halting the sinking slabs.

Subducting slabs can stagnate in the lower mantle. High-pressure laboratory experiments show that the viscosity of a dominant mantle phase increases dramatically at shallow lower-mantle depths, which could cause the slabs to halt their descent.

Ice shelves in West Antarctica have been shown to melt where warm circumpolar deep water enters a sub-shelf cavity. A bathymetric reconstruction of Totten Glacier in East Antarctica suggests that the same process may be at work there.

Deep abyssal clay sediments in organic-poor regions of the ocean present challenging conditions for life. Techniques for identifying cells at extremely low concentrations demonstrate that aerobic microbes are found throughout these deep clays in as much of 37% of the global ocean.

Totten Glacier has the largest thinning rate in East Antarctica. A derivation of the sea floor bathymetry reveals entrances to the ice cavity beneath the glacier that could allow deep warm water to enter and enhance basal melting.

The El Niño/Southern Oscillation modulates global weather and climate. Analyses of large-scale environmental indices show that it also affects the frequency of tornado and hail events in the central United States, which may help with predictability.

The depth of oxygen penetration and microbial activity in marine sediments varies by region. Sediment cores from the South Pacific Gyre host oxygen and aerobic microbial communities to at least 75 metres below the sea floor.

Flowing water shapes most of Earth's canyons, obscuring the contributions of other erosional mechanisms. A comparison of adjacent canyons with and without wind shielding shows that wind can amplify canyon incision on windblown Earth and Mars.

Precipitation patterns in the western Pacific changed at the onset of the Little Ice Age. A synthesis of precipitation reconstructions suggests that this change resulted from a contraction of the intertropical convergence zone.

Water is considered the primary agent that erodes and shapes bedrock canyons. Analyses of canyon morphology in the central Andes suggest that abrasion by wind can amplify canyon incision and reshape canyons on Earth—and possibly on Mars.

Arsenic in aquifers is transformed by biological and abiotic reactions. Field measurements and laboratory experiments suggest that the microbial methylation of arsenic contributes to subsurface arsenic cycling.

Droughts can cause dry-season productivity to decline in tropical forests. This decline occurs when precipitation is below 2,000 mm yr⁻¹, resulting in insufficient subsurface water storage to maintain constant production through the dry season.

Pinpointing when Earth's core formed depends on the extent of metal–silicate equilibration in the mantle. Vaporization and recondensation of impacting planetesimal cores during accretion may reconcile disparate lines of evidence.

Differentiated planetesimals may have delivered iron-rich material to Earth in giant impacts at the end of accretion. Impact experiments suggest that the planetesimals’ iron cores vaporized, aiding dispersal and mixing into Earth’s mantle.

Some biological particles act as ice nuclei in the atmosphere, affecting clouds and precipitation. Cloud-chamber experiments demonstrate that cellulose particles can act as efficient ice-nucleating particles in supercooled clouds.

Ore bodies buried deep in Earth's crust could meet increasing global demands for metals, but mining them would be costly and could damage the environment. Reinventing an ancient technology for bioleaching metals could provide a solution.

Modern societies require more and more metals, not least for renewable energy generation. Scientists from a range of disciplines are needed to prospect for ore deposits and provide a basis for sustainable exploration.