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Search for water outgassing of (1) Ceres near perihelion

Rousselot, P. and Opitom, C. and Jehin, E. and Hutsemékers, D. and Manfroid, J. and Villarreal, M. N. and Li, J.-Y. and Castillo-Rogez, J. and Russell, C. T. and Vernazza, P. and Marsset, M. and Roth, L. and Dumas, C. and Yang, B. and Prettyman, T. H. and Mousis, O. (2019) Search for water outgassing of (1) Ceres near perihelion. Astronomy and Astrophysics, 628 . Art. No. A22. ISSN 0004-6361.

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Context. (1) Ceres is the largest body in the main asteroid belt and one of the most intriguing objects in the solar system, in part because of the discovery of water outgassing by the Herschel Space Observatory (HSO) and its still-debated origin. Ceres was the target of NASA’s Dawn spacecraft for 3.5 yr, which achieved a detailed characterization of the dwarf planet. The possible influence of the local flux of solar energetic particles (SEP) on the production of a Cerean exosphere and water vapor has been suggested, in addition to the sublimation of water ice that depends on the temperature, meaning the heliocentric distance. Aims. We used the opportunity of both the perihelion passage of (1) Ceres in April 2018, and the presence of Dawn in its vicinity (for measuring the SEP flux in real time) to check the influence of heliocentric distance and SEP flux on water outgassing. Methods. We searched for OH emission lines near the limb of Ceres in the near-UV with the UVES spectrograph mounted on the 8-m ESO Very Large Telescope. Two spectra were recorded when Ceres was close to its perihelion, in February 2018, and with Dawn spacecraft orbiting Ceres. It was possible to simultaneously measure energetic particles around Ceres at the time of our observations. Results. Our observations did not permit detection of OH emission lines to a very high sensitivity level. This level is estimated to correspond to a global water production rate of Q_(H₂O) ∽ 2 × 10²⁶ molecules s⁻¹, similar to the water production rate derived from HSO observations. The solar energetic particles flux measured around Ceres was negligible at the time of these observations. Conclusions. Our observations support the idea that heliocentric distance (i.e., the sublimation of water ice) does not play a major role in the water emission from Ceres. This production rate could be either related to SEP events or to other mechanisms, possibly of endogenic origin.

Item Type:Article
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Russell, C. T.0000-0003-1639-8298
Additional Information:© 2019 P. Rousselot et al. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 19 April 2019; Accepted 13 June 2019; Published online 30 July 2019. Based on observations collected at the European Southern Observatory under ESO program 2100.C-5038(A). E.J. and D.H are Belgian FNRS Senior Research Associates.
Group:Thirty Meter Telescope
Funding AgencyGrant Number
Fonds de la Recherche Scientifique (FNRS)UNSPECIFIED
Subject Keywords:minor planets, asteroids: individual: (1) Ceres
Record Number:CaltechAUTHORS:20200311-132823440
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Official Citation:Search for water outgassing of (1) Ceres near perihelion. P. Rousselot, C. Opitom, E. Jehin, D. Hutsemékers, J. Manfroid, M. N. Villarreal, J.-Y. Li, J. Castillo-Rogez, C. T. Russell, P. Vernazza, M. Marsset, L. Roth, C. Dumas, B. Yang, T. H. Prettyman and O. Mousis. A&A, 628 (2019) A22; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101857
Deposited By: Tony Diaz
Deposited On:11 Mar 2020 21:11
Last Modified:11 Mar 2020 21:11

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