Short-term variability on the surface of (1) Ceres⋆. A changing amount of water ice?
Journal
Date Issued
2015
Author(s)
•
Kaňuchová, Z.
•
•
Fornasier, S.
•
Barucci, M. A.
•
Lantz, C.
•
•
Strazzulla, G.
Description
We thank A.S. Rivkin and P. Vernazza for kindly providing their spectral data. The research of Z.K. is supported by VEGA – The Slovack Agency for Science, Grant No. 2/0032/14. This program was supported by the French national space agency CNES and French INSU – PNP program.
Abstract
Context. The dwarf planet (1) Ceres - next target of the NASA Dawn mission - is the largest body in the asteroid main belt. Although several observations of this body have been performed so far, the presence of surface water ice is still questioned.
Aims: Our goal is to better understand the surface composition of Ceres and to constrain the presence of exposed water ice.
Methods: We acquired new visible and near-infrared spectra at the Telescopio Nazionale Galileo (La Palma, Spain), and reanalyzed literature spectra in the 3-μm region.
Results: We obtained the first rotationally resolved spectroscopic observations of Ceres at visible wavelengths. Visible spectra taken one month apart at almost the same planetocentric coordinates show a significant slope variation (up to 3%/103Å). A faint absorption centered at 0.67 μm, possibly due to aqueous alteration, is detected in a subset of our spectra. The various explanations in the literature for the 3.06-μm feature can be interpreted as due to a variable amount of surface water ice at different epochs.
Conclusions: The remarkable short-term temporal variability of the visible spectral slope and the changing shape of the 3.06-μm band can be hints of different amounts of water ice exposed on the surface of Ceres. This would agree with the recent detection by the Herschel Space Observatory of localized and transient sources of water vapor over this dwarf planet.
Aims: Our goal is to better understand the surface composition of Ceres and to constrain the presence of exposed water ice.
Methods: We acquired new visible and near-infrared spectra at the Telescopio Nazionale Galileo (La Palma, Spain), and reanalyzed literature spectra in the 3-μm region.
Results: We obtained the first rotationally resolved spectroscopic observations of Ceres at visible wavelengths. Visible spectra taken one month apart at almost the same planetocentric coordinates show a significant slope variation (up to 3%/103Å). A faint absorption centered at 0.67 μm, possibly due to aqueous alteration, is detected in a subset of our spectra. The various explanations in the literature for the 3.06-μm feature can be interpreted as due to a variable amount of surface water ice at different epochs.
Conclusions: The remarkable short-term temporal variability of the visible spectral slope and the changing shape of the 3.06-μm band can be hints of different amounts of water ice exposed on the surface of Ceres. This would agree with the recent detection by the Herschel Space Observatory of localized and transient sources of water vapor over this dwarf planet.
Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.Appendices are available in electronic form at http://www.aanda.org
Volume
575
Start page
L1
Issn Identifier
0004-6361
Ads BibCode
2015A&A...575L...1P
Rights
open.access
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