News & Views

Surface water is known to shape the formation and growth of valleys and channels. However, in some geologic settings, groundwater seeping upwards is important for the development of channel networks.

Nutrient-rich tropical and agricultural soils release vast quantities of the highly potent greenhouse gas nitrous oxide. New measurements show that vegetation-free patches of tundra in subarctic Europe can also emit large quantities of this gas.

According to one controversial idea, increases in atmospheric greenhouse-gas concentrations due to human activities can be detected as early as several thousand years ago. Eight years after the publication of this hypothesis, controversy continues.

Ice ages in the North Pacific Ocean and the Southern Ocean were marked by low productivity. Accumulating evidence indicates that strong stratification restricted the supply of nutrients from the deep ocean to the algae of the sunlit surface in these regions.

Within just three years, a 2,000-km stretch of the plate boundary tracing the Indonesian archipelago slipped in four earthquakes. Studies of past and present seismic activity in the region show a complex, but organized pattern of earthquake supercycles, the latest of which has not been completed.

The causes of recent dynamic thinning of Greenland's outlet glaciers have been debated. Realistic simulations suggest that changes at the marine fronts of these glaciers are to blame, implying that dynamic thinning will cease once the glaciers retreat to higher ground.

Surface ozone levels are expected to be high in polluted regions during summer months. Observations from Wyoming in February 2008 indicate that equally high concentrations of ozone can be produced during winter.

The exact mechanism used by microorganisms to produce the neurotoxin methyl mercury is unclear. The latest laboratory studies point to the amino acid cysteine as an important aid for the uptake of inorganic mercury and its transformation to methyl mercury in Geobacter sulfurreducens.

Climate models predict that increasing greenhouse gas levels will invigorate the circulation in the upper atmosphere. But a close look at observations of the age of stratospheric air over 30 years reveals no acceleration in the circulation.

Meteorites frequently bombarded the surface of the early Earth. Could these impacts have provided the energy and materials to form the basic building blocks of life?

The lack of deep mixing in the subpolar North Atlantic Ocean for over a decade has raised concerns that climate warming may already be affecting the ocean circulation. A vigorous convection event last winter shows that the system holds some surprises yet.

Sub-surface oceans probably exist on several large satellites of Jupiter and Saturn. An analysis of Europa's tides suggests that some of the Rossby waves are resonantly enhanced by the obliquity, producing sufficient heat and flow to keep the ocean liquid.

Measurements of directional travel speed of seismic waves constrain flow in the upper mantle. Laboratory experiments suggest that high pressure can change the mantle's mineral alignment, leading to a 90° offset in the direction of the fastest seismic waves.

Volcanism in the enormous Tharsis region on Mars migrated from south to north. Numerical modelling suggests that this migration as well as the current location of the region can be explained by net rotation of the lithosphere relative to the mantle.

The North Atlantic Oscillation has shown high variability over the past few decades. A two-hundred-year-long temperature reconstruction from a Bermuda coral suggests a link to recent climate warming.

The Earth's known rock reservoirs contain more radiogenic lead than expected on average. Mantle-derived rocks with highly unradiogenic lead — as discovered in the Horoman massif — may bear witness to a previously unsampled, complementary reservoir.