Properties of craters on the Achaia region of Asteroid (21) Lutetia

Auger, Anne; Bouley, Sylvain; Jordá, L.; Groussin, O.; Lamy, P.; Baratoux, D.

doi:10.1016/j.icarus.2014.10.014

Cited by 23 publications

(47 citation statements)

References 43 publications

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“…1. The smooth deposits in other areas (notably Anubis and Imhotep; Auger et al 2015) have a completely different appearance with possible layering that has not been observed elsewhere.…”

Section: Surface Depositsmentioning

confidence: 83%

Redistribution of Particles Across the Nucleus of Comet 67p/Churyumov-Gerasimenko

Thomas¹,

Davidsson²,

El-Maarry³

et al. 2016

Geological Society of America Abstracts With Programs

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Context. We present an investigation of the surface properties of areas on the nucleus of comet 67P/Churyumov-Gerasimenko. Aims. We aim to show that transport of material from one part of the cometary nucleus to another is a significant mechanism that influences the appearance of the nucleus and the surface thermal properties. Methods. We used data from the OSIRIS imaging system onboard the Rosetta spacecraft to identify surface features on the nucleus that can be produced by various transport mechanisms. We used simple calculations based on previous works to establish the plausibility of dust transport from one part of the nucleus to another. Results. We show by observation and modeling that "airfall" as a consequence of non-escaping large particles emitted from the neck region of the nucleus is a plausible explanation for the smooth thin deposits in the northern hemisphere of the nucleus. The consequences are also discussed. We also present observations of aeolian ripples and ventifacts. We show by numerical modeling that a type of saltation is plausible even under the rarified gas densities seen at the surface of the nucleus. However, interparticle cohesive forces present difficulties for this model, and an alternative mechanism for the initiation of reptation and creep may result from the airfall mechanism. The requirements on gas density and other parameters of this alternative make it a more attractive explanation for the observations. The uncertainties and implications are discussed.

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“…1. The smooth deposits in other areas (notably Anubis and Imhotep; Auger et al 2015) have a completely different appearance with possible layering that has not been observed elsewhere.…”

Section: Surface Depositsmentioning

confidence: 83%

Redistribution of Particles Across the Nucleus of Comet 67p/Churyumov-Gerasimenko

Thomas¹,

Davidsson²,

El-Maarry³

et al. 2016

Geological Society of America Abstracts With Programs

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“…We briefly describe here the similarities to Wild 2 and Hartley 2 while the similarities between the circular features on Tempel 1 and those observed in the Imhotep region (Fig. 4) are addressed in detail by Auger et al (2015). Circular and semicircular flat-floored features are observed mainly in the Seth region and appear to be composed of weakly consolidated materials that occasionally collapse forming debris and talus-like deposits (these should not be confused with the "active pits" (see Vincent et al 2015, and Table 1) that show generally larger d/D ratios).…”

Section: Morphological Comparison To Other Jupitermentioning

confidence: 92%

“…The smooth material thins out toward the Apis/Atum side and gives way to a terrain dominated by circular filled and unfilled structures, which are further investigated in Auger et al (2015). Imhotep is the only region on the imaged surface with these types of structures at this time.…”

Section: Imhotepmentioning

confidence: 94%

“…The Imhotep region is geologically one of the most diverse regions on the nucleus (see Auger et al 2015). It is dominated by a smooth bouldered surface (see Pajola et al 2015) overlying rougher terrain, which appears to be enclosed in part by Khepry (Fig.…”

Section: Imhotepmentioning

confidence: 99%

“…Some of the features introduced here are discussed more extensively in other papers in this Rosetta special feature. For instance, Auger et al (2015) present a detailed geomorphological investigation Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

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Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images

El‐Maarry

Thomas

Giacomini

et al. 2015

A&A

Self Cite

166

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Aims. The OSIRIS camera onboard the Rosetta spacecraft has been acquiring images of the comet 67P/Churyumov-Gerasimenko (67P)'s nucleus at spatial resolutions down to ∼0.17 m/px ever since Aug. 2014. These images have yielded unprecedented insight into the morphological diversity of the comet's surface. This paper presents an overview of the regional morphology of comet 67P. Methods. We used the images that were acquired at orbits ∼20-30 km from the center of the comet to distinguish different regions on the surface and introduce the basic regional nomenclature adopted by all papers in this Rosetta special feature that address the comet's morphology and surface processes. We used anaglyphs to detect subtle regional and topographical boundaries and images from close orbit (∼10 km from the comet's center) to investigate the fine texture of the surface. Results. Nineteen regions have currently been defined on the nucleus based on morphological and/or structural boundaries, and they can be grouped into distinctive region types. Consolidated, fractured regions are the most common region type. Some of these regions enclose smooth units that appear to settle in gravitational sinks or topographically low areas. Both comet lobes have a significant portion of their surface covered by a dusty coating that appears to be recently placed and shows signs of mobilization by aeolian-like processes. The dusty coatings cover most of the regions on the surface but are notably absent from a couple of irregular large depressions that show sharp contacts with their surroundings and talus-like deposits in their interiors, which suggests that short-term explosive activity may play a significant role in shaping the comet's surface in addition to long-term sublimation loss. Finally, the presence of layered brittle units showing signs of mechanical failure predominantly in one of the comet's lobes can indicate a compositional heterogeneity between the two lobes.

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Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

Fornasier

Hasselmann

Barucci

et al. 2015

A&A

Self Cite

215

147

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Context. The Rosetta mission of the European Space Agency has been orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014 and is now in its escort phase. A large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted are onboard Rosetta. Aims. We present results for the photometric and spectrophotometric properties of the nucleus of 67P derived from the OSIRIS imaging system, which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). The observations presented here were performed during July and the beginning of August 2014, during the approach phase, when OSIRIS was mapping the surface of the comet with several filters at different phase angles (1.3• -54• ). The resolution reached up to 2.1 m/px. Methods. The OSIRIS images were processed with the OSIRIS standard pipeline, then converted into I/F radiance factors and corrected for the illumination conditions at each pixel using the Lommel-Seeliger disk law. Color cubes of the surface were produced by stacking registered and illumination-corrected images. Furthermore, photometric analysis was performed both on disk-averaged photometry in several filters and on disk-resolved images acquired with the NAC orange filter, centered at 649 nm, using Hapke modeling. Results. The disk-averaged phase function of the nucleus of 67P shows a strong opposition surge with a G parameter value of −0.13 ± 0.01 in the HG system formalism and an absolute magnitude H v (1, 1, 0) = 15.74 ± 0.02 mag. The integrated spectrophotometry in 20 filters covering the 250−1000 nm wavelength range shows a red spectral behavior, without clear absorption bands except for a potential absorption centered at ∼290 nm that is possibly due to SO 2 ice. The nucleus shows strong phase reddening, with disk-averaged spectral slopes increasing from 11%/(100 nm) to 16%/(100 nm) in the 1.3• −54• phase angle range. The geometric albedo of the comet is 6.5 ± 0.2% at 649 nm, with local variations of up to ∼16% in the Hapi region. From the disk-resolved images we computed the spectral slope together with local spectrophotometry and identified three distinct groups of regions (blue, moderately red, and red). The Hapi region is the brightest, the bluest in term of spectral slope, and the most active surface on the comet. Local spectrophotometry shows an enhancement of the flux in the 700−750 nm that is associated with coma emissions.

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Properties of craters on the Achaia region of Asteroid (21) Lutetia

Cited by 23 publications

References 43 publications

Redistribution of Particles Across the Nucleus of Comet 67p/Churyumov-Gerasimenko

Redistribution of Particles Across the Nucleus of Comet 67p/Churyumov-Gerasimenko

Regional surface morphology of comet 67P/Churyumov-Gerasimenko from Rosetta/OSIRIS images

Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

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