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| Titel |
Comet 67P: Thermal Maps and Local Properties as Derived from Rosetta/VIRTIS data |
| VerfasserIn |
Federico Tosi, Maria Teresa Capria, Fabrizio Capaccioni, Gianrico Filacchione, Stephane Erard, Cedric Leyrat, Dominique Bockelee-Morvan, Maria Cristina De Sanctis, Andrea Raponi, Mauro Ciarniello, Bernard Schmitt, Gabriele Arnold, Stefano Mottola, Sergio Fonti, Ernesto Palomba, Andrea Longobardo, Priscilla Cerroni, Giuseppe Piccioni, Pierre Drossart, Ekkehard Kuehrt |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250111496
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| Publikation (Nr.) |
 EGU/EGU2015-11625.pdf |
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| Zusammenfassung |
| Comet 67P is shown to be everywhere rich in organic materials with little to no water ice
visible on the surface. In the range of heliocentric distances from 3.59 to 2.74 AU,
daytime observed surface temperatures retrieved from VIRTIS data are overall
comprised in the range between 180 and 220 K, which is incompatible with large
exposures of water ice and is consistent with a low-albedo, organics-rich surface. The
accuracy of temperature retrieval is as good as a few K in regions of the comet
unaffected by shadowing or limb proximity. Maximum temperature values as high
as 230 K have been recorded in very few places. The highest values of surface
temperature in the early Mapping phase were obtained in August 2014, during
observations at small phase angles implying that the observed surface has a large
predominance of small incidence angles, and local solar times (LST) centered around
the maximum daily insolation. In all cases, direct correlation with topographic
features is observed, i.e.Âlargest temperature values are generally associated with
the smallest values of illumination angles. So far, there is no evidence of thermal
anomalies, i.e.Âplaces of the surface that are intrinsically warmer or cooler than
surrounding terrains observed at the same local solar time and under similar solar
illumination.
For a given LST, the maximum temperature mainly depends on the solar incidence angle and
on surface properties such as thermal inertia and albedo. Since VIRTIS is able to observe the
same point of the surface on various occasions under different conditions of solar
illumination and LST, it is possible to reconstruct the temperature of that point at different
times of the comet’s day, thus building diurnal profiles of temperature that are useful to
constrain thermal inertia.
The availability of spatially-resolved, accurate temperature observations, significantly spaced
out in local solar time, provides clues to the physical structure local features, which
complements the compositional investigation based on imaging spectroscopy data collected
at shorter wavelengths.
In the VIRTIS thermal images, a note of great interest is provided by the ‘neck’ of the comet
close to the ‘body’, where, because of the concave shape, the ‘head’ casts prominent shadows
on some areas when they experience maximum daily insolation. This is a place potentially
subjected to considerable thermal stresses. We evaluate both the spatial thermal
gradients and the temporal thermal gradients, providing implications for the surface
structure.
Acknowledgements: The authors would like to thank the following institutions and agencies,
which supported this work: Italian Space Agency (ASI - Italy), Centre National d’Etudes
Spatiales (CNES- France), Deutsches Zentrum für Luft- und Raumfahrt (DLR-Germany),
National Aeronautic and Space Administration (NASA-USA) Rosetta Program, Science and
Technology Facilities Council (UK). VIRTIS has been built by a consortium, which includes
Italy, France and Germany, under the scientific responsibility of the Istituto di Astrofisica e
Planetologia Spaziali of INAF, Italy, which guides also the scientific operations. The VIRTIS
instrument development has been funded and managed by ASI, with contributions from
Observatoire de Meudon financed by CNES, and from DLR. The computational
resources used in this research have been supplied by INAF-IAPS through the DataWell
project. |
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