Geomorphology of the Imhotep region on comet 67P/Churyumov-Gerasimenko from OSIRIS observations

Auger, A.-T.; Groussin, O.; Jordá, L.; Bouley, Sylvain; Gaskell, R. W.; Lamy, Philippe; Capanna, Claire; Thomas, N.; Pommerol, Antoine; Sierks, H.; Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, Jessica; A’Hearn, Michael F.; Barucci, Maria Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Cremonese, G.; Deppo, Vania Da; Davidsson, B.; Debei, S.; Cecco, M. De; El‐Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Ip, W.-H.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Forgia, F. La; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Marchi, S.; Marzari, F.; Massironi, Matteo; Michalik, H.; Naletto, G.; Oklay, N.; Pajola, M.; Sabau, L.; Tubiana, C.; Vincent, Jean‐Baptiste; Wenzel, K.‐P.

doi:10.1051/0004-6361/201525947

Cited by 65 publications

(19 citation statements)

References 49 publications

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“…At heliocentric distances <2.7 AU, thermallydriven sublimation of water ice can occur with great efficiency. At the same time mechanical stresses that produce fractures in the upper few meters of the ice matrix can occur due to diurnal thermal expansions and contractions (Lachenbruch, 1962) or due to pressure build-up caused by volatiles outgassing in inclusions and voids (Tauber and Kürth, 1987;Auger et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

The global surface composition of 67P/CG nucleus by Rosetta/VIRTIS. (I) Prelanding mission phase

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Capaccioni

Ciarniello

et al. 2016

Icarus

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From August to November 2014 the Rosetta orbiter has performed an extensive observation campaign aimed at the characterization of 67P/CG nucleus properties and to the selection of the Philae landing site. The campaign led to the production of a global map of the illuminated portion of 67P/CG nucleus. During this prelanding phase the comet's heliocentric distance decreased from 3.62 to 2.93 AU while Rosetta was orbiting around the nucleus at distances between 100 to 10 km. VIRTIS-M, the Visible and InfraRed Thermal Imaging Spectrometer -Mapping channel (Coradini et al., 2007) onboard the orbiter, has acquired 0.25-5.1 µm hyperspectral data of the entire illuminated surface, e.g. the north hemisphere and the equatorial regions, with spatial resolution between 2.5 and 25 m/pixel. I/F spectra have been corrected for thermal emission removal in the 3.5-5.1 µm range and for surface's photometric response. The resulting reflectance spectra have been used to compute several Cometary Spectral Indicators (CSI): single scattering albedo at 0.55 µm, 0.5-0.8 µm and 1.0-2.5 µm spectral slopes, 3.2 µm organic material and 2.0 µm water ice band parameters (center, depth) with the aim to map their spatial distribution on the surface and to study their temporal variability as the nucleus moved towards the Sun. Indeed, throughout the investigated period, the nucleus surface shows a significant increase of the single scattering albedo along with a decrease of the 0.5-0.8 and 1.0-2.5 µm spectral slopes, indicating a flattening of the reflectance. We attribute the origin of this effect to the partial removal of the dust layer caused by the increased contribution of water sublimation to the gaseous activity as comet crossed the frost-line. The regions more active at the time of these observations, like Hapi in the neck/north pole area, appear brighter, bluer and richer in organic material than the rest of the large and small lobe of the nucleus. The parallel coordinates method (Inselberg, 1985) has been used to identify associations between average values of the spectral indicators and the properties of the geomorphological units as defined by Thomas et al. (2015); El-Maarry et al. (2015). Three classes have been identified (smooth/active areas, dust covered areas and depressions), which can be clustered on the basis of the 3.2 µm organic material's band depth, while consolidated terrains show a high variability of the spectral properties resulting being distributed across all three classes. These results show how the spectral variability of the nucleus surface is more variegated than the morphological classes and that 67P/CG surface properties are dynamical, changing with the heliocentric distance and with activity processes.

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Section: Introductionmentioning

confidence: 99%

The global surface composition of 67P/CG nucleus by Rosetta/VIRTIS. (I) Prelanding mission phase

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Capaccioni

Ciarniello

et al. 2016

Icarus

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“…This Imhotep-based bright feature is recorded in several epochs. The bright spot is close to the isolated accumulation basin and to the small roundish features interpreted by Auger et al 2015 as ancient degassing conduits. It is located at the base of what appears to be an open trench surrounded by steep small scarps.…”

Section: Analysis Of the Exposed H 2 O Ice Spotsmentioning

confidence: 99%

“…By applying illumination correction using the Lommer-Seeliger disk law, the reflectance of the bright spot increased by a factor of 2 for the sequence on 25 March, unlike other cases of bright features, with the exception of spot 8. Auger et al 2015 as a fractured accumulation basin. Similar to the bright patches of spot 4, this patch also seems to be formed by a freshly exposed area of a highly fractured material.…”

Section: Analysis Of the Exposed H 2 O Ice Spotsmentioning

confidence: 99%

Detection of exposed H₂O ice on the nucleus of comet 67P/Churyumov-Gerasimenko

Barucci

Filacchione

Fornasier

et al. 2016

A&A

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Context. Since the orbital insertion of the Rosetta spacecraft, comet 67P/Churyumov-Gerasimenko (67P/C-G) has been mapped by OSIRIS camera and VIRTIS spectro-imager, producing a huge quantity of images and spectra of the comet's nucleus. Aims. The aim of this work is to search for the presence of H 2 O on the nucleus which, in general, appears very dark and rich in dehydrated organic material. After selecting images of the bright spots which could be good candidates to search for H 2 O ice, taken at high resolution by OSIRIS, we check for spectral cubes of the selected coordinates to identify these spots observed by VIRTIS. Methods. The selected OSIRIS images were processed with the OSIRIS standard pipeline and corrected for the illumination conditions for each pixel using the Lommel-Seeliger disk law. The spots with higher I/F were selected and then analysed spectrophotometrically and compared with the surrounding area. We selected 13 spots as good targets to be analysed by VIRTIS to search for the 2 µm absorption band of water ice in the VIRTIS spectral cubes. Results. Out of the 13 selected bright spots, eight of them present positive H 2 O ice detection on the VIRTIS data. A spectral analysis was performed and the approximate temperature of each spot was computed. The H 2 O ice content was confirmed by modeling the spectra with mixing (areal and intimate) of H 2 O ice and dark terrain, using Hapke's radiative transfer modeling. We also present a detailed analysis of the detected spots.

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“…[48,150]; examining the connection between these bodies and the inner Solar System [151] and the Earth [90]; and addressing the general questions of complex disc chemistry in a primordial nebula [152]. …”

Section: Development Of Cometary Activity Comparing With Pre-perihelmentioning

confidence: 99%

The Rosetta mission orbiter science overview: the comet phase

Taylor

Altobelli

Buratti

et al. 2017

Phil. Trans. R. Soc. A.

100

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The international Rosetta mission was launched in 2004 and consists of the orbiter spacecraft Rosetta and the lander Philae. The aim of the mission is to map the comet 67P/Churyumov–Gerasimenko by remote sensing, and to examine its environment in situ and its evolution in the inner Solar System. Rosetta was the first spacecraft to rendezvous with and orbit a comet, accompanying it as it passes through the inner Solar System, and to deploy a lander, Philae, and perform in situ science on the comet's surface. The primary goals of the mission were to: characterize the comet's nucleus; examine the chemical, mineralogical and isotopic composition of volatiles and refractories; examine the physical properties and interrelation of volatiles and refractories in a cometary nucleus; study the development of cometary activity and the processes in the surface layer of the nucleus and in the coma; detail the origin of comets, the relationship between cometary and interstellar material and the implications for the origin of the Solar System; and characterize asteroids 2867 Steins and 21 Lutetia. This paper presents a summary of mission operations and science, focusing on the Rosetta orbiter component of the mission during its comet phase, from early 2014 up to September 2016.This article is part of the themed issue ‘Cometary science after Rosetta’.

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Geomorphology of the Imhotep region on comet 67P/Churyumov-Gerasimenko from OSIRIS observations

Cited by 65 publications

References 49 publications

The global surface composition of 67P/CG nucleus by Rosetta/VIRTIS. (I) Prelanding mission phase

The global surface composition of 67P/CG nucleus by Rosetta/VIRTIS. (I) Prelanding mission phase

Detection of exposed H₂O ice on the nucleus of comet 67P/Churyumov-Gerasimenko

The Rosetta mission orbiter science overview: the comet phase

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Geomorphology of the Imhotep region on comet 67P/Churyumov-Gerasimenko from OSIRIS observations

Cited by 65 publications

References 49 publications

The global surface composition of 67P/CG nucleus by Rosetta/VIRTIS. (I) Prelanding mission phase

The global surface composition of 67P/CG nucleus by Rosetta/VIRTIS. (I) Prelanding mission phase

Detection of exposed H2O ice on the nucleus of comet 67P/Churyumov-Gerasimenko

The Rosetta mission orbiter science overview: the comet phase

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Detection of exposed H₂O ice on the nucleus of comet 67P/Churyumov-Gerasimenko