ALBERT

Description: The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument on board the Rosetta spacecraft has provided evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 +/- 0.003 at 0.55 micrometers), the spectral slopes in visible and infrared ranges (5 to 25 and 1.5 to 5% kA(-1)), and the broad absorption feature in the 2.9-to-3.6-micrometer range present across the entire illuminated surface are compatible with opaque minerals associated with nonvolatile organic macromolecular materials: a complex mixture of various types of carbon-hydrogen and/or oxygen-hydrogen chemical groups, with little contribution of nitrogen-hydrogen groups. In active areas, the changes in spectral slope and absorption feature width may suggest small amounts of water-ice. However, no ice-rich patches are observed, indicating a generally dehydrated nature for the surface currently illuminated by the Sun.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Capaccioni, F -- Coradini, A -- Filacchione, G -- Erard, S -- Arnold, G -- Drossart, P -- De Sanctis, M C -- Bockelee-Morvan, D -- Capria, M T -- Tosi, F -- Leyrat, C -- Schmitt, B -- Quirico, E -- Cerroni, P -- Mennella, V -- Raponi, A -- Ciarniello, M -- McCord, T -- Moroz, L -- Palomba, E -- Ammannito, E -- Barucci, M A -- Bellucci, G -- Benkhoff, J -- Bibring, J P -- Blanco, A -- Blecka, M -- Carlson, R -- Carsenty, U -- Colangeli, L -- Combes, M -- Combi, M -- Crovisier, J -- Encrenaz, T -- Federico, C -- Fink, U -- Fonti, S -- Ip, W H -- Irwin, P -- Jaumann, R -- Kuehrt, E -- Langevin, Y -- Magni, G -- Mottola, S -- Orofino, V -- Palumbo, P -- Piccioni, G -- Schade, U -- Taylor, F -- Tiphene, D -- Tozzi, G P -- Beck, P -- Biver, N -- Bonal, L -- Combe, J-Ph -- Despan, D -- Flamini, E -- Fornasier, S -- Frigeri, A -- Grassi, D -- Gudipati, M -- Longobardo, A -- Markus, K -- Merlin, F -- Orosei, R -- Rinaldi, G -- Stephan, K -- Cartacci, M -- Cicchetti, A -- Giuppi, S -- Hello, Y -- Henry, F -- Jacquinod, S -- Noschese, R -- Peter, G -- Politi, R -- Reess, J M -- Semery, A -- New York, N.Y. -- Science. 2015 Jan 23;347(6220):aaa0628. doi: 10.1126/science.aaa0628.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica (INAF), Rome, Italy. fabrizio.capaccioni@iaps.inaf.it. ; Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica (INAF), Rome, Italy. ; Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Observatoire de Paris/CNRS/Universite Pierre et Marie Curie[acute accent over last letter in "Universite"]/Universite Paris-Diderot, Meudon, France. ; Institute for Planetary Research, Deutsches Zentrum fur Luft- und Raumfahrt (DLR), Berlin, Germany. ; Universite Grenoble Alpes, CNRS, Institut de Planetologie et d'Astrophysique de Grenoble, Grenoble, France. ; Osservatorio di Capodimonte, INAF, Napoli, Italy. ; Bear Fight Institute, Winthrop, WA 98862, USA. ; University of California, Los Angeles, Los Angeles, CA 90095, USA. ; European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands. ; Institut d'Astrophysique Spatial, CNRS, Orsay, France. ; Dipartimento di Matematica e Fisica "Ennio De Giorgi," Universita del Salento, Italy. ; Space Research Centre, Polish Academy of Sciences, Warsaw, Poland. ; NASA Jet Propulsion Laboratory, Pasadena, CA 91109, USA. ; Space Physics Research Laboratory, The University of Michigan, Ann Arbor, MI 48109, USA. ; Universita di Perugia, Perugia, Italy. ; Lunar Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA. ; National Central University, Taipei, Taiwan. ; Departement of Physics, Oxford University, Oxford, UK. ; Institute for Planetary Research, Deutsches Zentrum fur Luft- und Raumfahrt (DLR), Berlin, Germany. Free University of Berlin, Institute of Geosciences, Malteserstrasse 74-100, Building Haus A, 12249 Berlin, Germany. ; Universita "Parthenope," Napoli, Italy. ; Helmholtz-Zentrum Berlin fur Materialien und Energie, Berlin, Germany. ; Osservatorio Astrofisico di Arcetri, INAF, Firenze, Italy. ; Agenzia Spaziale Italiana, Rome, Italy. ; NASA Jet Propulsion Laboratory, Pasadena, CA 91109, USA. Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA. ; Istituto di Radioastronomia, INAF, Bologna, Italy. ; Institut fur Optische Sensorsysteme, DLR, Berlin, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25613895" target="_blank"〉PubMed〈/a〉

Description: Observations of cometary nuclei have revealed a very limited amount of surface water ice, which is insufficient to explain the observed water outgassing. This was clearly demonstrated on comet 9P/Tempel 1, where the dust jets (driven by volatiles) were only partially correlated with the exposed ice regions. The observations of 67P/Churyumov-Gerasimenko have revealed that activity has a diurnal variation in intensity arising from changing insolation conditions. It was previously concluded that water vapour was generated in ice-rich subsurface layers with a transport mechanism linked to solar illumination, but that has not hitherto been observed. Periodic condensations of water vapour very close to, or on, the surface were suggested to explain short-lived outbursts seen near sunrise on comet 9P/Tempel 1. Here we report observations of water ice on the surface of comet 67P/Churyumov-Gerasimenko, appearing and disappearing in a cyclic pattern that follows local illumination conditions, providing a source of localized activity. This water cycle appears to be an important process in the evolution of the comet, leading to cyclical modification of the relative abundance of water ice on its surface.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉De Sanctis, M C -- Capaccioni, F -- Ciarniello, M -- Filacchione, G -- Formisano, M -- Mottola, S -- Raponi, A -- Tosi, F -- Bockelee-Morvan, D -- Erard, S -- Leyrat, C -- Schmitt, B -- Ammannito, E -- Arnold, G -- Barucci, M A -- Combi, M -- Capria, M T -- Cerroni, P -- Ip, W-H -- Kuehrt, E -- McCord, T B -- Palomba, E -- Beck, P -- Quirico, E -- VIRTIS Team -- England -- Nature. 2015 Sep 24;525(7570):500-3. doi: 10.1038/nature14869.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto di Astrofisica e Planetologia Spaziali - INAF, via del fosso del cavaliere 100, 00133 Rome, Italy. ; Institute for Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany. ; LESIA-Observatoire de Paris, CNRS, Universite Pierre et Marie Curie, Universite Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France. ; Universite Grenoble Alpes - CNRS Institut de Planetologie et Astrophysique de Grenoble, Batiment D de Physique, BP 53, 38041 Grenoble Cedex 9, France. ; University of California, Los Angeles, California 90095, USA. ; Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward Street, Ann Arbor, Michigan 48109, USA. ; National Central University, No. 300, Jhongda Road, Jhongli District, Taoyuan City, 32001 Taipei, Taiwan. ; Bear Fight Institute, 22 Fiddler's Road, Box 667, Winthrop, Washington 98862, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26399830" target="_blank"〉PubMed〈/a〉

Description: Aside from the well-known double helix, DNA can also adopt an alternative four-stranded structure known as G-quadruplex. Implications of such a structure in cellular processes, as well as its therapeutic and diagnostic applications, have been reported. The G-quadruplex structure is highly polymorphic, but so far, only right-handed helical forms have...