The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse

Pajola, M.; Höfner, Sebastian; Vincent, Jean‐Baptiste; Oklay, N.; Scholten, F.; Preusker, Frank; Mottola, S.; Naletto, G.; Fornasier, S.; Lowry, S. C.; Feller, C.; Hasselmann, P. H.; Güttler, C.; Tubiana, C.; Sierks, H.; Barbieri, C.; Lamy, Philippe; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, Jessica; A’Hearn, Michael F.; Barucci, M. A.; Bertaux, J.; Bertini, Ivano; Besse, S.; Boudreault, S.; Cremonese, G.; Deppo, Vania Da; Davidsson, B.; Debei, S.; Cecco, M. De; Deller, Jakob; Deshapriya, J. D. P.; El‐Maarry, M. R.; Ferrari, Sabrina; Ferri, F.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Hofmann, M.; Hviid, S. F.; Ip, W. H.; Jordá, L.; Knollenberg, J.; Kovács, Gábor; Kramm, J.-R.; Kührt, Ekkehard; Küppers, M.; Lara, L. M.; Lin, Z.-Y.; Lazzarin, M.; Lucchetti, Alice; Moreno, J. J. Lopez; Marzari, F.; Massironi, Matteo; Michalik, H.; Penasa, Luca; Pommerol, Antoine; Simioni, Emanuele; Thomas, N.; Tóth, I.; Baratti, Emanuele

doi:10.1038/s41550-017-0092

Cited by 120 publications

(71 citation statements)

References 46 publications

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“…These observations suggest that an upper layer of regolith is progressively removed in the months just prior to perihelion (see SOM), leaving behind only the largest boulders (cyan arrows in Figure e/f; Figure S3). We rule out mass wasting as the origin for these boulders, as we do not observe a corresponding change in the upslope cliff (Pajola et al, ). Post‐perihelion observations show a near‐reversion to the original featureless surface, which we attribute, in part, to deposition during polar night (Keller et al, ).…”

Section: Discovery and Migration Of Depression Scarpsmentioning

confidence: 82%

Migrating Scarps as a Significant Driver for Cometary Surface Evolution

Birch

Hayes

Umurhan

et al. 2019

Geophysical Research Letters

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Rosetta observations of 67P/Churyumov‐Gerasimenko (67P) reveal that most changes occur in the fallback‐generated smooth terrains, vast deposits of granular material blanketing the comet's northern hemisphere. These changes express themselves both morphologically and spectrally across the nucleus, yet we lack a model that describes their formation and evolution. Here we present a self‐consistent model that thoroughly explains the activity and mass loss from Hapi's smooth terrains. Our model predicts the removal of dust via reradiated solar insolation localized within depression scarps that are substantially more ice rich than previously expected. We couple our model with numerous Rosetta observations to thoroughly capture the seasonal erosion of Hapi's smooth terrains, where local scarp retreat gradually removes the uppermost dusty mantle. As sublimation‐regolith interactions occur on rocky planets, comets, icy moons, and Kuiper belt objects, our coupled model and observations provide a foundation for future understanding of the myriad of sublimation‐carved worlds.

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Section: Discovery and Migration Of Depression Scarpsmentioning

confidence: 82%

Migrating Scarps as a Significant Driver for Cometary Surface Evolution

Birch

Hayes

Umurhan

et al. 2019

Geophysical Research Letters

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“…Despite the fact that these airless bodies experience large diurnal temperature variations (on the order of ∼100 K), thermal stress weathering has long been presumed to be of little significance in the inner solar system. Within the last decade, thermal stress weathering has been revisited with greater rigour and is now suspected to play an important role in rock breakdown, regolith generation, crater degradation, and landscape evolution in Earth's deserts and cold regions (Hall, ; Lamp, Marchant, Mackay, & Head, ), Mars (Eppes, Willis, Molaro, Abernathy, & Zhou, ; Viles et al, ), Mercury (Molaro & Byrne, ), Moon (Mazrouei, Ali Lagoa, Delbo, Ghent, & Wilkerson, ; Molaro, Byrne, & Langer, ; Molaro, Byrne, & Le, ; Ruesch et al, ), near‐Earth asteroids (Delbo et al, ; Dombard, Barnouin, Prockter, & Thomas, ; Graves, Minton, Molaro, & Hirabayashi, ; Jewitt, ), and perhaps comets (Alí‐Lagoa, Delbo, & Libourel, ; El‐Maarry et al, ; Pajola et al, ; Shestakova & Tambovtseva, ; Tambovtseva, Grinin, & Kozlova, ).…”

Section: Introductionmentioning

confidence: 99%

Unraveling the Mechanics of Thermal Stress Weathering: Rate‐Effects, Size‐Effects, and Scaling Laws

et al. 2019

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Thermal stress weathering is now recognized to be an active and significant geomorphological process on airless bodies. This study aims to understand the key factors governing thermal stresses in rocks on airless bodies through extensive numerical calculations and analytic analyses. Microscopic (grain‐scale) thermal stresses are driven primarily by the maximum diurnal temperature variation at said depth. Macroscopic (rock‐scale) thermal stresses are more complex. For rock sizes larger than the thermal skin depth, macroscopic thermal stresses are driven primarily by second (and higher) order spatial gradients of temperature. For rock sizes smaller than the thermal skin depth, macroscopic thermal stresses are primarily driven by the ratio of rock size to thermal skin depth. Additionally, scaling relations for diurnal surface temperature variation, time‐rate‐of‐change of surface temperature, as well as peak microscopic (grain‐scale) and macroscopic (rock‐scale) thermal stresses are derived to provide a more accessible modeling tool. These scaling relations are remarkably accurate when compared to both the numerical calculations as well as three‐dimensional finite element calculations. The model formulation, results, and scaling relations provided here allow the estimation of diurnal temperatures and thermal stresses on rocks of various size and materials on airless bodies at any orbital distance with a broad spectrum of spin rates. Lastly, we postulate and confirm that there is a critical spin rate where macroscopic thermal stresses will be greatest.

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“…These observations suggest that cliff collapse is an important process in reshaping cometary surfaces (Britt et al, ; Pajola et al, ; Steckloff et al, ; Steckloff & Samarasinha, ). OSIRIS observations show a direct evidence of the occurrence of a cometary landslide, with the resulting production of a newly formed boulder talus located at the base of the scarp (see the Aswan case; Pajola et al, ). Several gravitational accumulation deposits of fragmented material have been identified on the surface of 67P associated with well‐defined scarps from which the material had detached (Figure ).…”

Section: Data Set: Identification Of Landslides On Comet 67pmentioning

confidence: 99%

“…(b) A landslide located in the Ash region with a H/L value of 0.62. (c) The Aswan cliff collapse (Pajola et al, ) consists of blocks with sizes >3 m. The H/L value for Aswan is equal to 0.85.…”

Section: Data Set: Identification Of Landslides On Comet 67pmentioning

confidence: 99%

The Rocky‐Like Behavior of Cometary Landslides on 67P/Churyumov‐Gerasimenko

Lucchetti

Penasa

Pajola

et al. 2019

Geophysical Research Letters

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Landslides have been identified on several solar system bodies, and different mechanisms have been proposed to explain their runout length. We analyze images from the Rosetta mission and report the global characterization of such features on comet 67P/Churyumov-Gerasimenko's surface. By assuming the height to runout length as an approximation for the friction coefficient of landslide material, we find that on comet 67P, this ratio falls between 0.50 and 0.97. Such unexpected high values reveal a rocky-type mechanical behavior that is much more akin to Earth dry landslides than to icy satellites' mass movements. This behavior indicates that 67P and likely comets in general are characterized by consolidated materials possibly rejecting the idea that they are fluffy aggregates. The variability of the runout length among 67P landslides can be attributed to the different volatile content located in the top few meters of the cometary crust, which can drive the mass movement.

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The pristine interior of comet 67P revealed by the combined Aswan outburst and cliff collapse

Abstract: The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record.

Cited by 120 publications

References 46 publications

Migrating Scarps as a Significant Driver for Cometary Surface Evolution

Migrating Scarps as a Significant Driver for Cometary Surface Evolution

Unraveling the Mechanics of Thermal Stress Weathering: Rate‐Effects, Size‐Effects, and Scaling Laws

The Rocky‐Like Behavior of Cometary Landslides on 67P/Churyumov‐Gerasimenko

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