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GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 166-4
Presentation Time: 9:00 AM-6:30 PM

SURFACE COMPOSITION OF CERES QUADRANGLE AC-4 INVESTIGATED BY THE DAWN MISSION


COMBE, Jean-Philippe1, MCCORD, Thomas B.1, SINGH, Sandeep1, DE SANCTIS, Maria Cristina2, AMMANNITO, E.3, CARROZZO, Filippo Giacomo4, CIARNIELLO, M.4, FRIGERI, Alessandro4, RAPONI, A.4, TOSI, Federico2, ZAMBON, Francesca2, SCULLY, Jennifer E.C.5, IEVA, Simone6, FULCHIGNONI, Marcello7, RAYMOND, Carol A.5 and RUSSELL, Christopher T.3, (1)Bear Fight Institute, P.O. Box 667, 22 Fiddler's Rd, Winthrop, WA 98862, (2)INAF - Istituto Nazionale di Astrofisica, IAPS - Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100, Rome, I-00133, Italy, (3)Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA, (4)INAF - Istituto Nazionale di Astrofisica, IAPS, IAPS - Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100, Rome, I-00133, Italy, (5)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, (6)OAR - Osservatorio Astronomico di Roma, INAF - Istituto Nazionale di Astorifisica, Via Frascati 33, Monteporizo Catone, 00078, Italy; LESIA - Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, Section de Meudon, 5, place Jules Janssen, Meudon, 92195, France, (7)LESIA - Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique, Observatoire de Paris, Section de Meudon, 5, place Jules Janssen, Meudon, 92195, France, ssingh@bearfightinstitute.com

The objective is to determine the surface composition of Ceres quadrangle Ac-4 (22°-66°N; 180°-270°E) using remote-sensing data from the Dawn mission [1] and interpret the geological and physical processes that can explain the observations. This quadrangle takes its name from the crater Ezinu (the largest within the limits of this region). The surface of this quadrangle is heavily cratered [2]. Because of that, the northernmost regions include deep shadows, especially the north-facing wall of fresh impact craters, which is a limitation when interpreting images and reflectance spectra.

The albedo calculated from images acquired by the Framing Camera (FC) is a very uniform within this quadrangle, with a few exceptions: 1) Low-albedo materials that are likely ejecta from the northern rim of Occator and from other small craters including one inside Ezinu, 2) Small areas with albedo higher than average including the southern rim of Ezinu and one fresh crater (unnamed) at 61.4°N, 221.5°E.

The Visible and InfraRed mapping spectrometer (VIR) is sensitive to absorption bands due to OH in phyllosilicates at 2.7 µm and ammoniated phyllosilicates at 3.06 µm [3]. The most extreme variations are observed in Occator ejecta (where the two absorption bands are strong) in contrast with the floor of Occator. Generally, fresh craters exhibit materials that have relatively weak phyllosilicate absorption bands, such as the southern rim of Ezinu and the unnamed crater at 61.4°N, 221.5°E. In addition, that particular crater contains H2O-rich materials [4] that are associated to mass-wasting.

We plan to focus on the following topics.

1- Perform an analysis of the composition of fresh craters in order to detect possible variations between the craters and to determine whether the composition of fresh craters is representative of the rest of the surface.

2- Investigate whether the H2O-rich area is associated to a distinctive mineralogy, and make comparisons with Oxo, where H2O has also been found [5]?

3- Measure the extent of ejecta from Occator and compare the results with those from geological mapping [6].

References

1. Russell C. T. et al., 2011, SSR 163

2. De Sanctis M.C. et al.,2011, SSR 163

3. De Sanctis et al., 2015, Nature 528.

4. Combe J-Ph. et al., 2016, GSA (this meeting)

5. Combe J-Ph. et al., 2016, LPSC #1820

6. Scully et al., Icarus, submitted

Session No. 166--Booth# 345

T159. Ceres' Surface Composition as an Indication of Interior Evolution (Posters)
Monday, 26 September 2016: 9:00 AM-6:30 PM
Exhibit Hall E/F (Colorado Convention Center)
Geological Society of America Abstracts with Programs. Vol. 48, No. 7
doi: 10.1130/abs/2016AM-281963
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