NEWS Titan may have Sea-level rise accelerating in 25-year record subsurface flow CLIMATE Analysis of 25 years data with ground truth from tide of data from US and European gauges. MOONS The seas on Saturn’s satellites and tide gauges shows “This is almost certainly a moon Titan behave like the that the rate of sea level rise has conservative estimate,” said oceans on Earth: they track the increased from 2.5 mm per year in Steve Nerem of the University of geoid. Their common elevations the 1990s to 3.4 mm per year today. Colorado Boulder, a member of suggest that Titan has some sort About half the global mean NASA’s Sea level Change team of subsurface liquid o fl w system sea level rise of 7 cm over the past and lead author of the paper like aquifers on Earth. 25 years has come from thermal published in Proceedings of the The conclusions are based on expansion of the oceans as the National Academy of Sciences. “Our a new topographic map of Titan world warms; the rest is from extrapolation assumes that sea using data from the NASA–ESA melting ice on land. The research level continues to change in the Cassini–Huygens mission, by team used climate models to future as it has over the last 25 a team led by Paul Corlies, of account for the effects of volcanic years. Given the large changes we Cornell University. They found eruptions and other data sets to Global patterns of sea-level rise based are seeing in the ice sheets today, that Titan’s three hydrocarbon determine the El Nino/La Nina on 25 years of satellite data. (NASA that’s not likely.” seas share a common equipoten effects and combined the satellite GSFC/K Mersmann) http://go.nasa.gov/2BY3iP5 tial surface, forming a sea level as Earth’s oceans do. This implies o fl w from one to the other in the subsurface. Map of magnetic field Researchers also tracked the elevations of existing lakes and at centre of our galaxy features interpreted as dry lakes; MILKY WAY Swirling clouds of gas and dust map out within a watershed, the dry lakes the magnetic field around the supermassive black hole were always at higher elevations, at the heart of the Milky Way. A team of researchers just as on Earth. This again sug led by Pat Roche of the University of Cardiff made the gests liquid hydrocarbons at a map using data from the Gran Telescopio Canarias. The common level in the sub surface. team used the infrared camera CanariCam to track the The results were published polarization of the light, indicating the pattern of the in two papers in Geophysical magnetic field, shown as lines in this image, around the Research Letters by Corlies et al. black hole. The image covers a region just over 2 light- and Hayes et al. years across. Colour indicates the intensity of the infrared http://bit.ly/2ovVP2e light from warm dust particles; bright stars to the left of http://bit.ly/2F0H5T9 centre are linked by streams of gas and dust, following the magnetic field. Elsewhere the dusty filaments do not follow the magnetic field and it is notable that the Swirling motions stars do not ae ff ct the overall magnetic field. Roche et al. published their work in Monthly Notices of the RAS. in early galaxies http://bit.ly/2CNGMoJ ALMA Galaxies formed 12.9 billion years ago, just 800 million years after the Big Bang, show signs of Seismic tomography reveals subducting slabs rotation like younger galaxies. TECTONICS The Mediterranean closer to the surface, and may Two high redshift galaxies at region has a history of damag help to unravel which faults are redshifts of 6.8540 ± 0.0003 and ing earthquakes linked to the active and likelier to give rise to 6.8076 ± 0.0002 sample the epoch collision between the African and earthquakes in future. of reionization, when hydrogen European plates. Seismic tomog It also explains episodes in the spectroscopic data is obscure. raphy is now providing a better recent geological past in which Renske Smit from the University picture of the subduction behind the Mediterranean Sea dried out. of Cambridge and colleagues the seismic hazard. “The deep friction between the used the Atacama Large Milli Seismic tomography tracks the slab and the mantle due to slab metre–submillimetre Array in paths of earthquake waves and dragging explains how the North Chile to measure the C ii line reconstructs the varying rock A view from the north of the shapes of Moroccan seaways between (157.4 µm). “We saw that the gas properties in three dimensions. the eastward-subducting African slab, the Atlantic Ocean and the was spinning around the central Cool subducting slabs show up in as it moves beneath Spain and the Mediterranean Sea were closed region of the galaxy,” said Smit, the warmer mantle, for example. Mediterranean Sea. around six million years ago,” speaking at the 231st meeting of This work, published by Wim said Douwe van Hinsbergen, the American Astronomical Soci Spakman of the University of subducting towards the east, the geologist at Utrecht University ety in January this year. “We did Utrecht and colleagues in Nature movement of Africa is also push and co author. “This caused the not expect to see this in the early Geosciences, shows a slab being ing it north. The African plate Mediterranean Sea area to dry universe. We expected chaotic subducted steeply towards the behaves as if largely connected out, creating thick layers of rock movements.” east, reaching 700 km depth to the European plate around the salt and gypsum.” This is called The main message is that some below the Mediterranean Sea Straits of Gibraltar. the Messinian Salinity Crisis; the early galaxies were mature and between Africa and Spain. Key to This complex pattern of slab drag identie fi d beneath the forming rotating discs akin to their model is the drag between movement, rather than a simple Straits of Gibraltar explains what galaxies like the Milky Way. Smit the slab and the surround subduction zone, gives rise to drove this phenomenon. et al. published in Nature. ing mantle. While the slab is different regional fault patterns http://go.nature.com/2GTy3nx http://go.nature.com/2COCtta A&G • April 2018 • Vol. 59 • aandg.org 2.9 Downloaded from https://academic.oup.com/astrogeo/article-abstract/59/2/2.9/4935762 by Ed 'DeepDyve' Gillespie user on 16 March 2018
Astronomy & Geophysics – Oxford University Press
Published: Apr 1, 2018
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