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  • 1
    Publication Date: 2013-11-08
    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〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2012-11-07
    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〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2012-05-15
    Description: Vesta's surface is characterized by abundant impact craters, some with preserved ejecta blankets, large troughs extending around the equatorial region, enigmatic dark material, and widespread mass wasting, but as yet an absence of volcanic features. Abundant steep slopes indicate that impact-generated surface regolith is underlain by bedrock. Dawn observations confirm the large impact basin (Rheasilvia) at Vesta's south pole and reveal evidence for an earlier, underlying large basin (Veneneia). Vesta's geology displays morphological features characteristic of the Moon and terrestrial planets as well as those of other asteroids, underscoring Vesta's unique role as a transitional solar system body.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jaumann, R -- Williams, D A -- Buczkowski, D L -- Yingst, R A -- Preusker, F -- Hiesinger, H -- Schmedemann, N -- Kneissl, T -- Vincent, J B -- Blewett, D T -- Buratti, B J -- Carsenty, U -- Denevi, B W -- De Sanctis, M C -- Garry, W B -- Keller, H U -- Kersten, E -- Krohn, K -- Li, J-Y -- Marchi, S -- Matz, K D -- McCord, T B -- McSween, H Y -- Mest, S C -- Mittlefehldt, D W -- Mottola, S -- Nathues, A -- Neukum, G -- O'Brien, D P -- Pieters, C M -- Prettyman, T H -- Raymond, C A -- Roatsch, T -- Russell, C T -- Schenk, P -- Schmidt, B E -- Scholten, F -- Stephan, K -- Sykes, M V -- Tricarico, P -- Wagner, R -- Zuber, M T -- Sierks, H -- New York, N.Y. -- Science. 2012 May 11;336(6082):687-90. doi: 10.1126/science.1219122.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉German Aerospace Center, Institute of Planetary Research, Berlin, Germany. ralf.jaumann@dlr.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22582254" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Gillespie et al. concur with our interpretation that certain lobate equatorial and mid-latitude features on Mars are due to debris-covered glaciers formed largely during past periods of increased spin-axis obliquity, when climate regimes favoured snow and ice accumulation and glacial ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the base of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice-rich glacier-like viscous flow and sublimation. Together with new ...
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