The highly active Anhur–Bes regions in the 67P/Churyumov–Gerasimenko comet: results from OSIRIS/ROSETTA observations - Archive ouverte HAL Access content directly
Journal Articles Monthly Notices of the Royal Astronomical Society Year : 2017

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

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Philippe Lamy
  • Function : Author
  • PersonId : 994769
Jean-Loup Bertaux
  • Function : Author
  • PersonId : 914210
Gabriele Cremonese
  • Function : Author
  • PersonId : 1005814
Olivier Groussin
  • Function : Author
  • PersonId : 837612
Pedro J. Gutiérrez
  • Function : Author
  • PersonId : 880386
Laurent Jorda
Michael Küppers
Nilda Oklay
  • Function : Author
  • PersonId : 976656
Maurizio Pajola
  • Function : Author
  • PersonId : 987591
Nicolas Thomas
Imre Toth
  • Function : Author

Abstract

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.
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Dates and versions

insu-01574238 , version 1 (13-11-2020)

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Sonia Fornasier, Clément Feller, J.-C. Lee, Sabrina Ferrari, Matteo Massironi, et al.. The highly active Anhur–Bes regions in the 67P/Churyumov–Gerasimenko comet: results from OSIRIS/ROSETTA observations. Monthly Notices of the Royal Astronomical Society, 2017, 469 (Suppl_2), pp.S93 - S107. ⟨10.1093/mnras/stx1275⟩. ⟨insu-01574238⟩
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