title: Ammoniated phyllosilicates with a likely outer Solar System origin on (1) Ceres.
abstract: 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.
authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.initials: MC
authors.lastname: De Sanctis
authors.affiliation: 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.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.lastname: Raponi
authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.|Southwest Research Institute, 1050 Walnut Street, Boulder, Colorado 80302, USA.
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authors.lastname: Marchi
authors.affiliation: Bear Fight Institute, 22 Fiddler's Road, PO Box 667, Winthrop, Washington 98862, USA.
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authors.lastname: McCord
authors.affiliation: Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996-1410, USA.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.affiliation: Istituto di Astrofisica e Planetologia Spaziali, INAF, Via del Fosso del Cavaliere 100, 00133 Roma, Italy.
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authors.lastname: Zambon
authors.affiliation: Bear Fight Institute, 22 Fiddler's Road, PO Box 667, Winthrop, Washington 98862, USA.
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authors.affiliation: Planetary Science Institute, Tucson, Arizona 85719-2395, USA.
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authors.affiliation: Institute of Planetary Research, German Aerospace Center (DLR), Rutherfordstrasse 2, 12489 Berlin, Germany.
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authors.lastname: Jaumann
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
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authors.initials: LA
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authors.affiliation: Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA.
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authors.affiliation: Planetary Science Institute, Tucson, Arizona 85719-2395, USA.
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authors.affiliation: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA.
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