Deep convection in the tropics is observed generally above a threshold for sea surface temperatures of about 26–28 °C. An analysis of satellite observations of tropical rainfall shows that the threshold has varied in the past 30 years in parallel with tropical mean sea surface temperatures. The image shows cumulus convection developing over the Pacific Ocean surface near Tuvalu. Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center, ISS013-E-67035.

Letter p842; News & Views p821

In the version originally published, the cover image was incorrectly described. The image shows cumulus convection developing over the Pacific Ocean surface near Tuvalu. Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center, ISS013-E-67035. This error has now been corrected in the HTML and PDF versions of the text.

The January 2010 Haiti earthquake was catastrophic, leaving more than one million people homeless. In this focus issue we have gathered articles — ranging from primary research to opinion pieces — that explore the physical processes responsible for the earthquake and the damage caused, as well as the humanitarian problems now facing the poorest country in the Western Hemisphere. The image shows the damage following the earthquake in a poor neighbourhood of Port-au-Prince, Haiti.

Photo courtesy of UNDP.

Letters p778, p783, p789 and p794; Article p800; Commentaries p739 and p740; News & Views p743; Backstory p808; online Backstory

Shifts in the position and intensity of the southern westerly winds recorded at single sites have been suggested to reflect uniform variation throughout the wind belt. Sedimentological analyses from the Andes suggest that changes in wind intensity in the core and northern margin of the westerlies were antiphased during the Holocene epoch. The image shows a tree in Tierra del Fuego, Argentina. Image courtesy of Marion Lely.

Letter p695; News & Views p666

The Trezona Formation of South Australia pre-dates the 635-million-year-old Marinoan glaciation. Fossils found at this location are up to several millimetres in size, and share morphological characteristics with sponge-grade animals. The image shows the polished surface of a Trezona Formation limestone rock containing fossils. Image from: Maloof Lab/Situ Studio

Article p653; News & Views p597

The composition, structure and evolution of the Moon's mantle is poorly constrained. A global survey of the Moon's surface, using the spectral profiler onboard the Japanese lunar explorer SELENE (Kaguya), identifies a number of exposures of olivine in concentric regions around lunar craters, with a possible mantle origin. The cover is a composite image of the region around Mare Orientale on the Moon, obtained with SELENE, and improved in resolution by a Clementine UVVIS 750-nm image. Colours are assigned to the principal components of the spectral data. Credit: JAXA/SELENE, NASA.

Letter p533; News & Views p517

Discovery of shear veins formed at unusually high angles of about 80 degrees relative to the greatest principal compressive stress in the Chrystalls Beach complex, New Zealand, suggests that slip can be facilitated by a pre-existing rock fabric under high fluid pressure. The image shows a photomicrograph of a quartz slickenfibre shear vein with crack-and-seal texture. The rock is cut parallel to the direction of crack opening and perpendicular to the shear surface. Image by Francesca Remitti.

Letter p482; News & Views p449

An episode of climate warming 200 million years ago was associated with catastrophic environmental changes. Experimental and palaeontological data suggest that a climate-driven shift to more flammable leaf shapes contributed to increased fire activity in East Greenland at this time. The image shows a scientific illustration of the luxuriant forest that covered East Greenland during the Late Triassic. Illustration by Marlene Hill Donnelly, commissioned by Jennifer McElwain.

Letter p426; News & Views p381

The loss of carbon dioxide from soils increases initially under climate warming, but tends to decline to control levels within a few years. Simulations of the soil carbon response to warming with a microbial enzyme model show that a decline in both microbial biomass and the production of degrading enzymes can explain this attenuation response. The image shows a coral fungus, emerging from the soil of a boreal forest about 20 km south of the town of Delta Junction, central Alaska. These fungi are important for soil carbon and nutrient cycling in this ecosystem. Image by Steven Allison.

Letter p336; News & Views p303

Ice clouds in the tropical tropopause layer have a key role in dehydrating air that is entering the stratosphere. Cloud-chamber measurements suggest that their high humidity can be explained if heterogeneous ice nucleation on glassy aerosols is a significant nucleation mechanism in this region. The image shows cirrus clouds over Neath, South Wales, UK. Image by Mike Davies.

Letter p233

Jupiter's large moons Ganymede and Callisto are similar in size and composition, but different in surface and interior characteristics. Simulations with geophysical models of core formation indicate that the difference in impact energy received by the two satellites during the period of late heavy bombardment can explain the dichotomy. The image shows Jupiter's twin satellites, Callisto and Ganymede, pictured against the planet's clouds. Image courtesy of NASA.

Letter p164

Water movement in upland humid watersheds from the soil surface to the stream is often described using the concept of translatory flow, which assumes that water at any soil depth is well mixed. A study of water isotopes in an Oregon watershed instead suggests that trees and streams tap into separate water reservoirs. This image shows a headwater stream at the H. J. Andrews Experimental Forest in western Oregon. Image courtesy of Matthew Betts.

Letter p100; News & Views p77

Microbially mediated oxidation of organic carbon is thought to drive the release of arsenic into groundwater. Hydrological and geochemical analyses suggest that pond water is the source of organic carbon in groundwater in Bangladesh. The image shows rice plants in Munshiganj, Bangladesh. Image courtesy of Sarah Jane White at Massachusetts Institute of Technology.Article p46; News & Views p5; Backstory p68