The highly active Anhur–Bes regions in the 67P/Churyumov–Gerasimenko comet: results from OSIRIS/ROSETTA observations

Fornasier, S.; Feller, C.; Lee, J.-C.; Ferrari, S.; Massironi, M.; Hasselmann, P. H.; Deshapriya, J. D. P.; Barucci, M. A.; Elmaarry, Mohamed Ramy; Giacomini, L.; Mottola, S.; Keller, H. U.; Ip, W.-H.; Lin, Z.-Y.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, Rafael; Koschny, D.; Rickman, H.; ... (2017). The highly active Anhur–Bes regions in the 67P/Churyumov–Gerasimenko comet: results from OSIRIS/ROSETTA observations. Monthly notices of the Royal Astronomical Society, 469(Suppl_2), S93-S107. Oxford University Press 10.1093/mnras/stx1275

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The Southern hemisphere of the 67P/Churyumov–Gerasimenko comet has become visible from Rosetta only since 2015 March. It was illuminated during the perihelion passage and therefore it contains the regions that experienced the strongest heating and erosion rates, thus exposing the sub-surface most pristine material. In this work we investigate, thanks to the OSIRIS images, the geomorphology, the spectrophotometry and some transient events of two Southern hemisphere regions: Anhur and part of Bes. Bes is dominated by outcropping consolidated terrain covered with fine particle deposits, while Anhur appears strongly eroded with elongated canyon-like structures, scarp retreats, different kinds of deposits and degraded sequences of strata indicating a pervasive layering. We discovered a new 140 m long and 10 m high scarp formed in the Anhur–Bes boundary during/after the perihelion passage, close to the area where exposed CO₂ and H₂O ices were previously detected. Several jets have been observed originating from these regions, including the strong perihelion outburst, an active pit and a faint optically thick dust plume. We identify several areas with a relatively bluer slope (i.e. a lower spectral slope value) than their surroundings, indicating a surface composition enriched with some water ice. These spectrally bluer areas are observed especially in talus and gravitational accumulation deposits where freshly exposed material had fallen from nearby scarps and cliffs. The investigated regions become spectrally redder beyond 2 au outbound when the dust mantle became thicker, masking the underlying ice-rich layers.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Elmaarry, Mohamed Ramy; Rodrigo, Rafael and Thomas, Nicolas

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering

ISSN:

0035-8711

Publisher:

Oxford University Press

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

14 Nov 2017 16:38

Last Modified:

14 Nov 2017 16:38

Publisher DOI:

10.1093/mnras/stx1275

BORIS DOI:

10.7892/boris.106272

URI:

https://boris.unibe.ch/id/eprint/106272

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