Torcello et Pise

Feller, Laurent

doi:10.3917/hyp.151.0355

Cited by 3 publications

(12 citation statements)

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“…Finally, to check whether we identify any seasonal albedo variation at the metre-scale, we compared the phase curve we retrieved for the same area visited by the 2015 February 14 flyby (Feller et al 2016). The whole flyby area is about 200 metres and is located on the Imhotep-Ash boundary.…”

Section: Comparison To Pre-perihelion Resultsmentioning

confidence: 99%

“…In this work, we have determined the phase curve of ice-rich features, which now provides a new comparison to the laboratory measurements. To verify any match between laboratory samples and cometary data, we decided to normalize all phase curves to α = 5 • due to the spectral mismatch (Feller et al 2016). We only selected measurements at i ≈ 0 • and we concentrated our comparison on α < 16 • , hence diminishing any possible contribution from macro-roughness due to large casting shadows.…”

Section: Comparison To Laboratory Measurementsmentioning

confidence: 99%

“…High steepness on the phase slope and absence of sharp OE is also observed among some dark objects of the Solar system (Shevchenko et al 2008(Shevchenko et al , 2012 and is generally interpreted as prevailing single-scattering effects. Additionally, previous Hapke modelling of OSIRIS images show a very broad SHOE-H, 1 indicating that 67P dust grains are possibly sufficiently opaque to disregard the strong contribution from inter-grain multiple scattering and the coherent-backscattering mechanism (Fornasier et al 2015;Ciarniello et al 2015;Feller et al 2016). Results from RADAR techniques also point to a dry and highly porous dust cover composed of irregular opaque micrometric particles (Kamoun et al 2014;Lethuillier et al 2016).…”

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confidence: 92%

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The opposition effect of 67P/Churyumov–Gerasimenko on post-perihelion Rosetta images

Hasselmann

Barucci

Fornasier

et al. 2017

Monthly Notices of the Royal Astronomical Society

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High-resolution OSIRIS/Rosetta images of 67P/Churyumov-Gerasimenko acquired on the night run of 2016 April 9-10 show, at large scale, an opposition effect (OE) spot sweeping across Imhotep as the phase angle ranges from 0 • to 17 • . In this work, we fitted the phase curve of the whole surface imaged as well as three particular features using both the linearexponential and Hapke models. These features encompass different types of spectral behaviour: a circular mesa, one venous structure and an assemblage of bright spots, going from red to blue colours. Both the Hapke and linear-exponential parameters indicate a stepwise sharpening of the OE from bright spots to circular mesa. Yet a very broad nonlinear phase curve is verified and no sign of sharp OE associated with a coherent-backscattering mechanism is observed. We estimate that the 67P surface is dominated by opaque, desiccated and larger-than-wavelength irregular grains. Veins and bright spots display photometric properties consistent with surfaces becoming slightly brighter as they are enriched by high-albedo ice grains. We also report the estimation of normal albedo for all cometary regions observed throughout the image sequence. Comparison to pre-perihelion results indicates that far better insolation of northern brighter regions, i.e. Hapi, Hathor and Seth, is sufficient to explain mismatches on the photometric parameters. However, metre-scale photometric analysis of the Imhotep-Ash boundary area advocates for mild darkening (<7 per cent) of the surface at local scale.

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Section: Comparison To Pre-perihelion Resultsmentioning

confidence: 99%

Section: Comparison To Laboratory Measurementsmentioning

confidence: 99%

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confidence: 92%

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The opposition effect of 67P/Churyumov–Gerasimenko on post-perihelion Rosetta images

Hasselmann

Barucci

Fornasier

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Strata are observed on cliffs as parallel linear features usually in alignment with cuesta ridges and terrace margins that are often repeated in staircase patterns (white arrows in Fig. 3a, Auger et al 2015;La Forgia et al 2015;Pajola et al 2015;Rickman et al 2015;Vincent et al 2015;Feller et al 2016;Giacomini et al 2016;Ip et al 2016). The strata can be used to interpret the internal structure of the comet (Massironi et al 2015).…”

Section: E T H O D O L O G Y a N D Data S E Tmentioning

confidence: 99%

Geomorphological mapping of comet 67P/Churyumov–Gerasimenko’s Southern hemisphere

Lee

Massironi

et al. 2016

Monthly Notices of the Royal Astronomical Society

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“…Then, images were photometrically corrected applying the Lommel-Seeliger disc law (Hapke 1993) and the geometric information about the illumination and observation angles were derived using the SPC shape model (Jorda et al 2016). In the relative spectrophotometry, the flux of a given region of interest is integrated over a 3×3 pixels box and normalized at 535 nm, following the same method described in Feller et al (2016), Deshapriya et al (2016), Fornasier et al (2017) and Oklay et al (2017).…”

Section: Data S E T a N D M E T H O D Smentioning

confidence: 99%

Geomorphological and spectrophotometric analysis of Seth's circular niches on comet 67P/Churyumov–Gerasimenko using OSIRIS images

Lucchetti

Pajola

Fornasier

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We provide a detailed geomorphological and spectrophotometric analysis of the circular niches located on the Seth region of 67P using OSIRIS images. The features can be related to landslide events that occurred on 67P and shaped its surface, as the recent Aswan cliff collapse detected in the same region. We therefore provide an analysis of the area pre-and post-perihelion suggesting that no specific changes have been observed. To assess this, after performing a geomorphological map of the area that allows us to identify different terrain units, we computed the boulders cumulative size frequency distribution (SFD) of the niches, before and after the perihelion passage. The niches SFDs are characterized by a similar trend with two different power-law indices within the same deposit: lower power-law value (between −2.3 and −2.7) for boulders smaller than 5 m and steeper power-law value (between −4.7 and −5.0) for boulders larger than 5 m. These trends suggest that smaller boulders have evolved and progressively have been depleted (lower power-law index), while bigger boulders are more representative of the event that generated the deposit and are less degraded. Then, we perform the spectrophotometric analysis of this region comparing pre-and post-perihelion results. We found colour changes within the area, in particular brighter patches related to the presence of exposed water ice mixed to the refractory materials have been detected in the post-perihelion images.

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Torcello et Pise

Cited by 3 publications

References 0 publications

The opposition effect of 67P/Churyumov–Gerasimenko on post-perihelion Rosetta images

The opposition effect of 67P/Churyumov–Gerasimenko on post-perihelion Rosetta images

Geomorphological mapping of comet 67P/Churyumov–Gerasimenko’s Southern hemisphere

Geomorphological and spectrophotometric analysis of Seth's circular niches on comet 67P/Churyumov–Gerasimenko using OSIRIS images

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