ALBERT

Description: Studies of the dwarf planet (1) Ceres using ground-based and orbiting telescopes have concluded that its closest meteoritic analogues are the volatile-rich CI and CM carbonaceous chondrites. Water in clay minerals, ammoniated phyllosilicates, or a mixture of Mg(OH)2 (brucite), Mg2CO3 and iron-rich serpentine have all been proposed to exist on the surface. In particular, brucite has been suggested from analysis of the mid-infrared spectrum of Ceres. But the lack of spectral data across telluric absorption bands in the wavelength region 2.5 to 2.9 micrometres--where the OH stretching vibration and the H2O bending overtone are found--has precluded definitive identifications. In addition, water vapour around Ceres has recently been reported, possibly originating from localized sources. Here we report spectra of Ceres from 0.4 to 5 micrometres acquired at distances from ~82,000 to 4,300 kilometres from the surface. Our measurements indicate widespread ammoniated phyllosilicates across the surface, but no detectable water ice. Ammonia, accreted either as organic matter or as ice, may have reacted with phyllosilicates on Ceres during differentiation. This suggests that material from the outer Solar System was incorporated into Ceres, either during its formation at great heliocentric distance or by incorporation of material transported into the main asteroid belt.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉De Sanctis, M C -- Ammannito, E -- Raponi, A -- Marchi, S -- McCord, T B -- McSween, H Y -- Capaccioni, F -- Capria, M T -- Carrozzo, F G -- Ciarniello, M -- Longobardo, A -- Tosi, F -- Fonte, S -- Formisano, M -- Frigeri, A -- Giardino, M -- Magni, G -- Palomba, E -- Turrini, D -- Zambon, F -- Combe, J-P -- Feldman, W -- Jaumann, R -- McFadden, L A -- Pieters, C M -- Prettyman, T -- Toplis, M -- Raymond, C A -- Russell, C T -- England -- Nature. 2015 Dec 10;528(7581):241-4. doi: 10.1038/nature16172.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy. ; Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA. ; Southwest Research Institute, 1050 Walnut Street, Boulder, Colorado 80302, USA. ; Bear Fight Institute, 22 Fiddler's Road, PO Box 667, Winthrop, Washington 98862, USA. ; Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996-1410, USA. ; Planetary Science Institute, Tucson, Arizona 85719-2395, USA. ; Institute of Planetary Research, German Aerospace Center (DLR), Rutherfordstrasse 2, 12489 Berlin, Germany. ; NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA. ; Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA. ; Institut de Recherche d'Astrophysique et Planetologie, Observatoire Midi Pyrenees, Universite Paul Sabatier, 14 Avenue E. Belin, 31400 Toulouse, France. ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26659184" target="_blank"〉PubMed〈/a〉

Description: Olivine is a major component of the mantle of differentiated bodies, including Earth. Howardite, eucrite and diogenite (HED) meteorites represent regolith, basaltic-crust, lower-crust and possibly ultramafic-mantle samples of asteroid Vesta, which is the lone surviving, large, differentiated, basaltic rocky protoplanet in the Solar System. Only a few of these meteorites, the orthopyroxene-rich diogenites, contain olivine, typically with a concentration of less than 25 per cent by volume. Olivine was tentatively identified on Vesta, on the basis of spectral and colour data, but other observations did not confirm its presence. Here we report that olivine is indeed present locally on Vesta's surface but that, unexpectedly, it has not been found within the deep, south-pole basins, which are thought to be excavated mantle rocks. Instead, it occurs as near-surface materials in the northern hemisphere. Unlike the meteorites, the olivine-rich (more than 50 per cent by volume) material is not associated with diogenite but seems to be mixed with howardite, the most common surface material. Olivine is exposed in crater walls and in ejecta scattered diffusely over a broad area. The size of the olivine exposures and the absence of associated diogenite favour a mantle source, but the exposures are located far from the deep impact basins. The amount and distribution of observed olivine-rich material suggest a complex evolutionary history for Vesta.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ammannito, E -- De Sanctis, M C -- Palomba, E -- Longobardo, A -- Mittlefehldt, D W -- McSween, H Y -- Marchi, S -- Capria, M T -- Capaccioni, F -- Frigeri, A -- Pieters, C M -- Ruesch, O -- Tosi, F -- Zambon, F -- Carraro, F -- Fonte, S -- Hiesinger, H -- Magni, G -- McFadden, L A -- Raymond, C A -- Russell, C T -- Sunshine, J M -- England -- Nature. 2013 Dec 5;504(7478):122-5. doi: 10.1038/nature12665. Epub 2013 Nov 6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto di Astrofisica e Planetologia Spaziali, INAF, 00133 Rome, Italy.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24196707" target="_blank"〉PubMed〈/a〉

Description: Localized dark and bright materials, often with extremely different albedos, were recently found on Vesta's surface. The range of albedos is among the largest observed on Solar System rocky bodies. These dark materials, often associated with craters, appear in ejecta and crater walls, and their pyroxene absorption strengths are correlated with material brightness. It was tentatively suggested that the dark material on Vesta could be either exogenic, from carbon-rich, low-velocity impactors, or endogenic, from freshly exposed mafic material or impact melt, created or exposed by impacts. Here we report Vesta spectra and images and use them to derive and interpret the properties of the 'pure' dark and bright materials. We argue that the dark material is mainly from infall of hydrated carbonaceous material (like that found in a major class of meteorites and some comet surfaces), whereas the bright material is the uncontaminated indigenous Vesta basaltic soil. Dark material from low-albedo impactors is diffused over time through the Vestan regolith by impact mixing, creating broader, diffuse darker regions and finally Vesta's background surface material. This is consistent with howardite-eucrite-diogenite meteorites coming from Vesta.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McCord, T B -- Li, J-Y -- Combe, J-P -- McSween, H Y -- Jaumann, R -- Reddy, V -- Tosi, F -- Williams, D A -- Blewett, D T -- Turrini, D -- Palomba, E -- Pieters, C M -- De Sanctis, M C -- Ammannito, E -- Capria, M T -- Le Corre, L -- Longobardo, A -- Nathues, A -- Mittlefehldt, D W -- Schroder, S E -- Hiesinger, H -- Beck, A W -- Capaccioni, F -- Carsenty, U -- Keller, H U -- Denevi, B W -- Sunshine, J M -- Raymond, C A -- Russell, C T -- England -- Nature. 2012 Nov 1;491(7422):83-6. doi: 10.1038/nature11561.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉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/23128228" target="_blank"〉PubMed〈/a〉

Description: Although water vapour is the main species observed in the coma of comet 67P/Churyumov-Gerasimenko and water is the major constituent of cometary nuclei, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far. The absence of large regions of exposed water ice seems a common finding on the surfaces of many of the comets observed so far. The nucleus of 67P/Churyumov-Gerasimenko appears to be fairly uniformly coated with dark, dehydrated, refractory and organic-rich material. Here we report the identification at infrared wavelengths of water ice on two debris falls in the Imhotep region of the nucleus. The ice has been exposed on the walls of elevated structures and at the base of the walls. A quantitative derivation of the abundance of ice in these regions indicates the presence of millimetre-sized pure water-ice grains, considerably larger than in all previous observations. Although micrometre-sized water-ice grains are the usual result of vapour recondensation in ice-free layers, the occurrence of millimetre-sized grains of pure ice as observed in the Imhotep debris falls is best explained by grain growth by vapour diffusion in ice-rich layers, or by sintering. As a consequence of these processes, the nucleus can develop an extended and complex coating in which the outer dehydrated crust is superimposed on layers enriched in water ice. The stratigraphy observed on 67P/Churyumov-Gerasimenko is therefore the result of evolutionary processes affecting the uppermost metres of the nucleus and does not necessarily require a global layering to have occurred at the time of the comet's formation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Filacchione, G -- De Sanctis, M C -- Capaccioni, F -- Raponi, A -- Tosi, F -- Ciarniello, M -- Cerroni, P -- Piccioni, G -- Capria, M T -- Palomba, E -- Bellucci, G -- Erard, S -- Bockelee-Morvan, D -- Leyrat, C -- Arnold, G -- Barucci, M A -- Fulchignoni, M -- Schmitt, B -- Quirico, E -- Jaumann, R -- Stephan, K -- Longobardo, A -- Mennella, V -- Migliorini, A -- Ammannito, E -- Benkhoff, J -- Bibring, J P -- Blanco, A -- Blecka, M I -- Carlson, R -- Carsenty, U -- Colangeli, L -- Combes, M -- Combi, M -- Crovisier, J -- Drossart, P -- Encrenaz, T -- Federico, C -- Fink, U -- Fonti, S -- Ip, W H -- Irwin, P -- Kuehrt, E -- Langevin, Y -- Magni, G -- McCord, T -- Moroz, L -- Mottola, S -- Orofino, V -- Schade, U -- Taylor, F -- Tiphene, D -- Tozzi, G P -- Beck, P -- Biver, N -- Bonal, L -- Combe, J-Ph -- Despan, D -- Flamini, E -- Formisano, M -- Fornasier, S -- Frigeri, A -- Grassi, D -- Gudipati, M S -- Kappel, D -- Mancarella, F -- Markus, K -- Merlin, F -- Orosei, R -- Rinaldi, G -- Cartacci, M -- Cicchetti, A -- Giuppi, S -- Hello, Y -- Henry, F -- Jacquinod, S -- Reess, J M -- Noschese, R -- Politi, R -- Peter, G -- England -- Nature. 2016 Jan 21;529(7586):368-72. doi: 10.1038/nature16190. Epub 2016 Jan 13.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉INAF-IAPS, Istituto di Astrofisica e Planetologia Spaziali, Rome, Italy. ; LESIA, Observatoire de Paris/CNRS/UPMC/Universite Paris-Diderot, Meudon, France. ; Institute for Planetary Research, DLR, Berlin, Germany. ; Universite Grenoble Alpes, CNRS, IPAG, Grenoble, France. ; INAF-Osservatorio di Capodimonte, Napoli, Italy. ; UCLA, Los Angeles, California, USA. ; European Space Agency-ESTEC, Noordwijk, The Netherlands. ; Institut d'Astrophysique Spatial CNRS, Orsay, France. ; Dipartimento di Matematica e Fisica "Ennio De Giorgi", Universita del Salento, Lecce, Italy. ; Space Research Centre, Polish Academy of Sciences, Warsaw, Poland. ; NASA JPL, Pasadena, California, USA. ; Space Physics Research Laboratory, The University of Michigan, Michigan, Ann Arbor, USA. ; Universita di Perugia, Perugia, Italy. ; Lunar Planetary Laboratory, University of Arizona, Tucson, Arizona, USA. ; National Central University, Taipei, Taiwan. ; Department of Physics, Oxford University, Oxford, UK. ; Bear Fight Institute, Winthrop, Washington, USA. ; Helmholtz-Zentrum Berlin fur Materialien und Energie, Berlin, Germany. ; INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy. ; Agenzia Spaziale Italiana, Rome, Italy. ; Istituto di Radioastronomia-INAF, Bologna, Italy. ; Institute of Optical Sensor Systems, DLR, Berlin, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26760209" target="_blank"〉PubMed〈/a〉