Short-term variability over the surface of (1) Ceres. A changing amount of water ice?
D. Perna, Z. Kauchov, S. Ieva, S. Fornasier, M. A. Barucci, C. Lantz, E. Dotto, G. Strazzulla
(Submitted on 17 Dec 2014)
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 (TNG, La Palma, Spain), and reanalyzed literature spectra in the 3-m 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 %/10$^3\AA$). A faint absorption centered at 0.67 m, possibly due to aqueous alteration, is detected in a subset of our spectra. The various explanations in the literature for the 3.06-m 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-m band, can be hints of different amounts of water ice exposed on the surface of Ceres. This would be in agreement with the recent detection by the Herschel Space Observatory of localized and transient sources of water vapour over this dwarf planet.
Comments: Resubmitted to A&A following referee comments
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1412.5318 [astro-ph.EP]
(or arXiv:1412.5318v1 [astro-ph.EP] for this version)
Submission history
From: Davide Perna
[v1] Wed, 17 Dec 2014 10:14:36 GMT (282kb)
