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The global surface composition of 67P/Churyumov-Gerasimenko nucleus by Rosetta/VIRTIS. II) Diurnal and seasonal variability

Journal
Date Issued
2016
Author(s)
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Kappel, D.
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Arnold, G.
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Barucci, M. A.
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Quirico, E.
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Kuehrt, E.
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Mottola, S.
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Erard, S.
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Bockelée-Morvan, D.
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Leyrat, C.
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Zinzi, A.
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Schmitt, B.
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Ip, W. -H.
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Salatti, M.
DOI
Abstract
VIRTIS-M observations of the nucleus of comet 67P/Churyumov-Gerasimenko acquired from 2014 August to 2015 May have been analysed to investigate surface temporal variability at both seasonal and diurnal scales. The measured reflectance spectra are studied by means of comet spectral indicators (CSI) such as slopes in the visible and infrared ranges, and 3.2 μm band area and band centre. CSI maps derived from data acquired at different heliocentric distances (from 3.62 to 1.72 au) along the inbound leg of the comet's orbit are used to infer surface water ice abundance. We measure a global scale enrichment of water ice from 2014 August to 2015 May across the body of the comet, along with variability at small spatial scale, possibly related with the local insolation conditions. Analysis of water ice diurnal variability is performed on 2014 August observations. Water ice appears at the border of receding shadows in the neck of the comet (Hapi), sublimating in less than 1 h, after exposure to sunlight. As similar variability is not observed in other regions of the comet, we interpreted this as the expression of a diurnal cycle of sublimation and re-condensation of water ice, triggered by sudden shadowing produced on the neck by the body and the head of the nucleus.
Volume
462
Start page
S443
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2016MNRAS.462S.443C
Rights
open.access
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