Characterization of the Abydos region through OSIRIS high-resolution images in support of CIVA measurements

¹ Center of Studies and Activities for Space, CISAS, “G. Colombo”, University of Padova, via Venezia 15, 35131 Padova, Italy
e-mail: alice.lucchetti@oapd.inaf.it
² INAF Osservatorio Astronomico di Padova, vic. dell’Osservatorio 5, 35122 Padova, Italy
³ Laboratoire d’Astrophysique de Marseille, UMR 7236, CNRS & Aix-Marseille Université, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
⁴ Institut d’Astrophysique Spatiale, CNRS/Univ. Paris Sud, 91440 Orsay Cedex, France
⁵ Department of Physics and Astronomy “G. Galilei”, University of Padova, Vic. Osservatorio 3, 35122 Padova, Italy
⁶ Geosciences Department, University of Padova, via G. Gradenigo 6, 35131 Padova, Italy
⁷ Physikalisches Institut der Universität Bern, Sidlerstr. 5, 3012 Bern, Switzerland
⁸ Max-Planck-Institut fuür Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
⁹ Centro de Astrobiologia, CSIC-INTA, 28850 Torrejon de Ardoz, Madrid, Spain
¹⁰ International Space Science Institute, Hallerstraße 6, 3012 Bern, Switzerland
¹¹ Scientific Support Office, European Space Research and Technology Centre/ESA, Keplerlaan 1, Postbus 299, 2201 AZ Noordwijk ZH, The Netherlands
¹² Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
¹³ PAS Space Research Center, Bartycka 18A, 00716 Warszawa, Poland
¹⁴ Institut fur Geophysik und extraterrestrische Physik, TU Braunschweig, 38106 Braunschweig, German
¹⁵ University of Maryland, Department of Astronomy, College Park, MD 20742-2421, USA
¹⁶ LESIA-Observatoire de Paris, CNRS, UPMC, Univ. Paris 06, Univ. Paris-Diderot, 5 Place J. Janssen, 92195 Meudon Principal Cedex, France
¹⁷ LATMOS, CNRS/UVSQ/IPSL, 11 Boulevard d’Alembert, 78280 Guyancourt, France
¹⁸ CNR-IFN UOS Padova LUXOR, via Trasea 7, 35131 Padova, Italy
¹⁹ Department of Industrial Engineering, University of Padova, via Venezia 1, 35131 Padova, Italy
²⁰ University of Trento, via Sommarive 9, 38123 Trento, Italy
²¹ INAF Osservatorio Astronomico di Trieste, via Tiepolo 11, 34014 Trieste, Italy
²² Instituto de Astrofísica de Andalucía-CSIC, 18008 Granada, Spain
²³ Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Planetenforschung, Rutherfordstraße 2, 12489 Berlin, Germany
²⁴ National Central University, Graduate Institute of Astronomy, 300 Chung-Da Rd, 32054 Chung-Li, Taiwan
²⁵ Operations Department, European Space Astronomy Centre/ESA, PO Box 78, 28691 Villanueva de la Canada, Madrid, Spain
²⁶ Department of Information Engineering, University of Padova, via Gradenigo 6/B, 35131 Padova, Italy

Received: 8 September 2015
Accepted: 13 November 2015

Abstract

Context. On 12 November 2014, the European mission Rosetta delivered the Philae lander on the nucleus of comet 67P/Churyumov-Gerasimenko (67P). After the first touchdown, the lander bounced three times before finally landing at a site named Abydos.

Aims. We provide a morphologically detailed analysis of the Abydos landing site to support Philae’s measurements and to give context for the interpretation of the images coming from the Comet Infrared and Visible Analyser (CIVA) camera system onboard the lander.

Methods. We used images acquired by the OSIRIS Narrow Angle Camera (NAC) on 6 December 2014 to perform the analysis of the Abydos landing site, which provided the geomorphological map, the gravitational slope map, the size-frequency distribution of the boulders. We also computed the albedo and spectral reddening maps.

Results. The morphological analysis of the region could suggest that Philae is located on a primordial terrain. The Abydos site is surrounded by two layered and fractured outcrops and presents a 0.02 km² talus deposit rich in boulders. The boulder size frequency distribution gives a cumulative power-law index of −4.0 + 0.3/−0.4, which is correlated with gravitational events triggered by sublimation and/or thermal fracturing causing regressive erosion. The average value of the albedo is 5.8% at λ₁ = 480.7 nm and 7.4% at λ₂ = 649.2 nm, which is similar to the global albedos derived by OSIRIS and CIVA, respectively.