|astro-news from Institute of Astronomy Library in Inoreader|
Planetary science: Titan's sea is super salty
Nature 511, 7509 (2014). doi:10.1038/511266b
Saturn's largest moon, Titan, has a buried ocean that is saltier than many seas on Earth.Titan, with its thick atmosphere and bodies of surface liquid, is of great interest to scientists looking for life beyond Earth. A team led by Giuseppe Mitri, of the
A deep crust–mantle boundary in the asteroid 4 Vesta
Nature 511, 7509 (2014). doi:10.1038/nature13499
Authors: Harold Clenet, Martin Jutzi, Jean-Alix Barrat, Erik I. Asphaug, Willy Benz & Philippe Gillet
The asteroid 4 Vesta was recently found to have two large impact craters near its south pole, exposing subsurface material. Modelling suggested that surface material in the northern hemisphere of Vesta came from a depth of about 20 kilometres, whereas the exposed southern material comes from a depth of 60 to 100 kilometres. Large amounts of olivine from the mantle were not seen, suggesting that the outer 100 kilometres or so is mainly igneous crust. Here we analyse the data on Vesta and conclude that the crust–mantle boundary (or Moho) is deeper than 80 kilometres.
Astrophysics: Survival of the largest
Nature 511, 7509 (2014). doi:10.1038/nature13640
Authors: Haley Gomez
Whether supernovae create most of the dust in the cosmos is a controversial question. Observations of a distant supernova have revealed signs of freshly formed dust, but the properties of the dust are unexpected. See Letter p.326
Rapid formation of large dust grains in the luminous supernova 2010jl
Nature 511, 7509 (2014). doi:10.1038/nature13558
Authors: Christa Gall, Jens Hjorth, Darach Watson, Eli Dwek, Justyn R. Maund, Ori Fox, Giorgos Leloudas, Daniele Malesani & Avril C. Day-Jones
The origin of dust in galaxies is still a mystery. The majority of the refractory elements are produced in supernova explosions, but it is unclear how and where dust grains condense and grow, and how they avoid destruction in the harsh environments of star-forming galaxies. The recent detection of 0.1 to 0.5 solar masses of dust in nearby supernova remnants suggests in situ dust formation, while other observations reveal very little dust in supernovae in the first few years after explosion. Observations of the spectral evolution of the bright SN 2010jl have been interpreted as pre-existing dust, dust formation or no dust at all. Here we report the rapid (40 to 240 days) formation of dust in its dense circumstellar medium. The wavelength-dependent extinction of this dust reveals the presence of very large (exceeding one micrometre) grains, which resist destruction. At later times (500 to 900 days), the near-infrared thermal emission shows an accelerated growth in dust mass, marking the transition of the dust source from the circumstellar medium to the ejecta. This provides the link between the early and late dust mass evolution in supernovae with dense circumstellar media.