The rapid increase in anthropogenic emissions of greenhouse gases necessitates the consideration of mechanisms for capturing and storing carbon dioxide. Recent work suggests that fluid or gaseous carbon dioxide can be injected into the Earth's crust and locked up as carbonate minerals to achieve near-permanent and secure sequestration. Image courtesy of John crouch.Progress Article p837; Editorial p809; Commentaries p813 and p815

The cause of high electrical conductivity in the middle crust beneath the Pacific Northwest region of the US is not clear. New electrical resistivity data reveal a connection between this regional conductor and a localized conductor beneath a prominent volcano in the region, suggesting that the anomalous conductivity is due to the presence of partial melts. The image shows the lava dome that began growing during the renewed eruptive phase of Mount St Helens (Autumn 2004–Winter 2008), seen glowing at midnight from the summit of Mount St Helens with Spirit Lake and Mount Rainier in the distance. Image courtesy of Tyson Fisher.Letter p785

The devastating Wenchuan earthquake in 2008 struck along a fault zone that displayed low rates of deformation. Analysis of GPS and InSAR data suggests that as structural barriers failed during a single earthquake, the rupture cascaded across multiple fault segments, which may explain the high magnitude of the event. The image was produced by Jianbao Sun, and it shows the surface deformation associated with the 2008 Wenchuan earthquake as inferred from Interferometric Synthetic Aperture Radar (InSAR).Article p718; Backstory p732

The Australian-Indonesian summer monsoon affects rainfall variability across the Indo-Pacific region. Reconstructions of monsoon strength from stalagmites show that precipitation increased from 11,000 to 7,000 years ago, as rising global sea level caused the flooding of the Indonesian continental shelf. The image shows speleothem deposits in Liang Luar cave formed by the precipitation of calcium carbonate. The photo was taken by Garry K. Smith.Letter p636; Backstory p664

Phosphorus is frequently the limiting nutrient in marine and terrestrial ecosystems. Analysis of lightning-derived glassy compounds from North America, Africa and Australia suggests that cloud-to-ground lightning increases the bioavailability of this nutrient. The image shows a 3.5-cm-wide fulgurite from Greensboro, North Carolina, USA. The centre of the fulgurite is filled with a blue glass. Photo taken by Virginia Pasek.

Letter p553; News & Views p538

Ammonia is a significant atmospheric pollutant, accelerating the formation of particulate matter and damaging aquatic and terrestrial ecosystems. Infrared measurements of ammonia concentrations, obtained by the IASI/MetOp satellite, suggest that ammonia emissions in the Northern Hemisphere have been markedly underestimated. The image shows atmospheric ammonia over the San Joaquin Valley, California in 2008, derived from infrared measurements made by the IASI space sounder. Background image from NASA-MODIS (Credit: L. Gonzalez and C. Deroo — LOA/USTL).

Letter p479; News & Views p461

Seismic anisotropy data for the Great Basin region of the western United States, coupled with tomographic images, help delineate a northeast-dipping lithospheric drip. Numerical experiments suggest that the drip could have formed owing to gravitational instability triggered by a density increase of as little as 1% and a temperature increase of about 10%. The image shows Wheeler Peak in Great Basin National Park, Nevada, USA. Photo by J. D. West, Silverheels Photography (www.fodoze.com).

Article p439; News & Views p381; Backstory p446

Particulate aerosols are thought to be the primary source of iron to the oceans, but the factors determining their solubility, and thus bioavailability, are unclear. X-ray absorption analysis reveals that speciation controls the solubility of iron in three large sources of aerosol iron. The image shows a dust storm off Alaska, taken by the Aqua satellite on 1 November 2006, at 22:15 UTC. Image credit: NASA/GSFC, MODIS Rapid Response.

Letter p337; News & Views p317

The oceans are becoming more acidic as they absorb anthropogenic carbon dioxide — this may limit the ability of marine organisms to secrete carbonate. A sediment-trap study shows that in the Southern Ocean the shell weights of a surface-dwelling single-celled organism with a calcite shell are lower than pre-industrial values, probably as a result of increasing ocean acidity. The image, obtained by scanning electron microscopy, shows a modern Globigerina bulloides shell recovered from a sediment trap in the Southern Ocean. Image courtesy of Antarctic Climate & Ecosystems Cooperative Research Centre.

Letter p276; Backstory p308

Groundwater seepage is expected to affect channel features, but its role remains controversial. Two linear response relationships that describe channel evolution from groundwater flux are sufficient to characterize seepage-driven channel networks, linking the dynamics of channel growth to channel morphology. The image shows a map of a network of channels created by the seepage of groundwater in the Florida Panhandle, obtained by airborne laser mapping. Steeply sloped valleys cut by the channels are about 100 metres wide and 20 metres deep. Image by Kyle M. Straub.

Letter p193; News & Views p165; online Backstory

Photochemical ozone production near the Earth's surface is considered to be a summertime, urban phenomenon. However, air-quality measurements in the rural Upper Green River basin, Wyoming, show rapid, diurnal photochemical production of ozone when air temperatures are as low as -17 °C. The image shows the Jonah natural gas field in Green River valley near the town of Pinedale on 12 May 2006. Photos by EcoFlight (www.ecoflight.info), courtesy of SkyTruth (www.skytruth.org).

Letter p120; News & Views p88; Backstory p152

Biological nitrogen fixation limits plant growth and carbon exchange at local-to-global scales. Long-term nutrient manipulation experiments in forests and short-term manipulation experiments in microcosms suggest that the micronutrient molybdenum, a component of the nitrogen-fixing enzyme nitrogenase, limits nitrogen fixation by asymbiotic bacteria in tropical soils in Panama. This image was taken by Lars Hedin in the dense tropical rainforest of the Barro Colorado Nature monument, Panama and shows a tree of the species Ceiba pentandra in the family Bombacaceae.

Letter p42