Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko

¹ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
² Max-Planck-Institut für Sonnensystemforschung, 37077 Göttingen, Germany
³ Department of Physics and Astronomy, Padova University, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁴ Centro de Astrobiologia (INTA-CSIC), 28691 Villanueva de la Canada, Madrid, Spain
⁵ International Space Science Institute, Hallerstrasse 6, 3012 Bern, Switzerland
⁶ Scientific Support Office, European Space Agency, 2201 Noordwijk, The Netherlands
⁷ Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
⁸ PAS Space Research Center, Bartycka 18A, 00716 Warszawa, Poland
⁹ Institute of Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin Germany
¹⁰ Institute for Geophysics and Extraterrestrial Physics, TU Braunschweig, 38106, Germany
¹¹ Department of Astronomy, University of Maryland, College Park, MD, 20742-2421, USA
¹² Laboratoire GEOPS (Géosciences Paris Sud), Bat. 509, Université Paris Sud, 91405 Orsay Cedex, France
¹³ LESIA, Obs. de Paris, CNRS, Univ Paris 06, Univ. Paris-Diderot, 5 place J. Janssen, 92195 Meudon, France
¹⁴ LATMOS, CNRS/UVSQ/IPSL, 11 boulevard d’Alembert, 78280 Guyancourt, France
¹⁵ Centro di Ateneo di Studi ed Attività Spaziali, “Giuseppe Colombo” (CISAS), University of Padova, via Venezia 15, 35131 Padova, Italy
¹⁶ Department of Industrial Engineering, University of Padova, 35131 Padova, Italy
¹⁷ CNR-IFN UOS Padova LUXOR, via Trasea 7, 35131 Padova, Italy
¹⁸ UNITN, Universit di Trento, via Mesiano, 77, 38100 Trento, Italy
¹⁹ Physikalisches Institut, Sidlerstr. 5, University of Bern, 3012 Bern, Switzerland
²⁰ INAF–Osservatorio Astronomico, via Tiepolo 11, 34143 Trieste, Italy
²¹ Instituto de Astrofisica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
²² Institute for Space Science, Nat. Central Univ., 300 Chung Da Rd., 32054 Chung-Li, Taiwan
²³ Operations Department, European Space Astronomy Centre/ESA, PO Box 78, 28691 Villanueva de la Canada, Madrid, Spain
²⁴ Centre for Astrophysics and Planetary Science, Schoold of Physical Sciences (SEPnet), The Univsersity of Kent, Canterbury, CT2 7NH, UK
²⁵ Southwest Research Institute, 1050 Walnut St., Boulder, CO 80302, USA
²⁶ INAF, Osservatorio Astronomico di Padova, 35122 Padova, Italy
²⁷ University of Padova, Department of Information Engineering, via Gradenigo 6/B, 35131 Padova, Italy
²⁸ Konkoly Observatory, 1525 Budapest, PO Box 67, Hungary

Received: 21 July 2015
Accepted: 8 September 2015

Abstract

Aims. We report on the first major temporal morphological changes observed on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko in the smooth terrains of the Imhotep region.

Methods. We used images of the OSIRIS cameras onboard Rosetta to follow the temporal changes from 24 May 2015 to 11 July 2015.

Results. The morphological changes observed on the surface are visible in the form of roundish features that are growing in size from a given location in a preferential direction at a rate of 5.6–8.1 × 10^-5 m s^-1 during the observational period. The location where the changes started and the contours of the expanding features are bluer than the surroundings, which suggests that ices (H₂O and/or CO₂) are exposed on the surface. However, sublimation of ices alone is not sufficient to explain the observed expanding features. No significant variations in the dust activity pattern are observed during the period of changes.