Volume 6 Issue 12, December 2013

The Chelyabinsk fireball highlighted the threat of asteroids and comets. But actually, for life on Earth, impacts may have once played the role of hero.

Volcanoes have been active under the West Antarctic Ice Sheet for millions of years, and there is evidence for recent activity. Now swarms of tiny earthquakes detected in 2010 and 2011 hint at current magma movement in the crust beneath the ice.

The surface of Mars is dominated by basalt that has undergone little magmatic evolution. However, minerals now identified in some ancient terrains suggest that extensive magma processing and intrusive volcanism were not uncommon on the red planet.

Global temperature rise since industrialization has not been uniform. A statistical analysis suggests that past changes in the rate of warming can be directly attributed to human influences, from economic downturns to the regulations of the Montreal Protocol.

Antarctic temperatures and atmospheric carbon dioxide levels generally co-varied at the end of glacial periods. Detailed analysis of an Antarctic ice core suggests a decoupling during the deglaciation 130,000 years ago, possibly linked to a strengthening of ocean circulation.

Significant quantities of the ozone and aerosol precursor isoprene are released into the atmosphere in densely forested regions of the world. Experimental observations suggest that the oxidation of isoprene in these pristine environments adds to the self-cleansing capacity of the atmosphere.

Following almost three decades of some certainty over how the Moon was formed, new geochemical measurements have thrown the planetary science community back into doubt. We are either modelling the wrong process, or modelling the process wrong.

The Indian Ocean Dipole is a key mode of interannual climate variability influencing much of Asia and Australia. A Review suggests that in response to greenhouse warming, mean conditions of the Indian Ocean will shift toward a positive dipole state, but with no overall shift in the frequency of positive and negative events as defined relative to the mean climate state.

The formation of the silicate mineral anorthosite is thought to require magmatic processes that are not expected on Mars because of its predominately mafic terrains. Localized spectral detections by the Mars Reconnaissance Orbiter are consistent with anorthosite, suggestive of ancient intrusive igneous processes similar to those active on Earth.

Felsic rocks have not been identified on Mars, a planet that lacks plate tectonics to drive the magmatic processes that lead to evolved silica-rich melts. Spectral observations by the Mars Reconnaissance Orbiter indicate that felsic lithologies occur at multiple localities on Mars and suggest prolonged magmatic activity on ancient Mars.

The pressures and temperatures experienced by material flung from craters following impact events are expected to preclude survival of organics. The preservation of biomarkers in impact glass from the Darwin crater in Tasmania suggests that organic matter can survive in the distal products of meteorite impact.

Field measurements have revealed much higher concentrations of hydroxyl radicals than expected in regions with high loads of the biogenic volatile organic compound isoprene. Results from isoprene oxidation experiments suggest that the additional recycling of radicals in the presence of isoprene contributes to hydroxyl radical enhancement in these regions.

Modern grasslands are dominated by grasses that use the C₄ photosynthetic pathway, and were established about 8 million years ago. A sediment record suggests that in southwestern Africa, the expansion of grasslands was associated with increasing aridity and fire activity, both of which favour grasses that use the C₄ pathway.

Several volcanoes exist in Marie Byrd Land, a highland range in West Antarctica, but none were thought to be currently active. Analysis of seismic data from the region shows that magma could be moving beneath the West Antarctic Ice Sheet, with potential implications for ice flow.

The flow of ductile rocks in the deep crust and uppermost mantle is thought to add stress to faults in the shallow crust, potentially bringing the faults closer to rupture. Measurements of fault offsets in the Italian Apennines show that earthquake recurrence is largely controlled by viscous flow of deeper rocks in localized zones.

The boundary between Earth’s rigid lithosphere and ductile asthenosphere is marked by a seismic discontinuity. Laboratory experiments on basaltic magmas show that melts should pond at pressures that correspond to the lithosphere–asthenosphere boundary. Thus, magma ponding could explain the observed seismic discontinuity.

Comets harbour the organic precursors of amino acids. High-velocity impact experiments into icy targets suggest that impacts involving icy planetary bodies could be a viable pathway to synthesize the complex organic compounds needed for life.

The causal connection between human activities and the evolution of climate warming over the past century is not fully understood. A state-of-the-art statistical analysis of time series of temperature and radiative forcing reveals that reductions in ozone-depleting substances and methane have contributed to the slow-down in warming since the late 1990s.

The predictability of heat waves in the mid-latitudes has been limited to the 10-day range of weather forecasts. An integration of a climate model that spans 12,000 years reveals a pattern in atmospheric planetary waves that tends to precede heat waves in the US, extending potential predictability to 20 days.

Glacial Termination II was marked by a rise in atmospheric CO₂ concentrations and global temperature. An analysis of air bubbles from an Antarctic ice core suggests that during the first phase of deglaciation, Antarctic temperature and atmospheric CO₂ concentrations increased together, whereas CO₂ lagged behind temperature rise during the second phase.

Recent research has highlighted problems with our present explanation for how the Moon formed in the giant impact of a large solar system body with the early Earth. In September 2013, London saw the latest in a series of landmark meetings debating theories of the Moon's origin, following others in 1984 (Kona, Hawaii) and 1998 (Monterey, California). These issues are now explored in a NatureCommentary,NatureNews & Views forum andNature GeoscienceNews & Views article. We also present a selection of recentNatureandNature Geosciencecontent related to the age, composition and origin of the Moon.