The southern hemisphere of 67P/Churyumov-Gerasimenko: Analysis of the preperihelion size-frequency distribution of boulders ≥7 m

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Publisher DOI
Abstract
Aims. We calculate the size-frequency distribution of the boulders on the southern hemisphere of comet 67P Churyumov-Gerasimenko (67P), which was in shadow before the end of April 2015. We compare the new results with those derived from the northern hemisphere and equatorial regions of 67P, highlighting the possible physical processes that lead to these boulder size distributions. Methods. We used images acquired by the OSIRIS Narrow Angle Camera (NAC) on 2 May 2015 at a distance of 125 km from the nucleus. The scale of this dataset is 2.3 m/px; the high resolution of the images, coupled with the favorable observation phase angle of 62 degrees, provided the possibility to unambiguously identify boulders ≥ 7 m on the surface of 67P and to manually extract them with the software ArcGIS. We derived the size-frequency distribution of the illuminated southern hemisphere. Results. We found a power-law index of -3.6 + 0.2 for the boulders on the southern hemisphere with a diameter range of 7-35 m. The power-law index is equal to the one previously found on northern and equatorial regions of 67P, suggesting that similar boulder formation processes occur in both hemispheres. The power-law index is related to gravitational events triggered by sublimation and/or thermal fracturing causing regressive erosion. In addition, the presence of a larger number of boulders per km² in the southern hemisphere, which is a factor of 3 higher with respect to the northern hemisphere, suggests that the southernmost terrains of 67P are affected by a stronger thermal fracturing and sublimating activity, hence possibly causing larger regressive erosion and gravitational events.
Date Issued
2016
Publication Type
Article
Subject(s)
Language(s)
en
Author(s)
Pajola, Maurizio
Lucchetti, Alice
Vincent, Jean-Baptiste
Oklay, Nilda
Bertini, Ivano
Naletto, Giampiero
Lazzarin, Monica
Massironi, Matteo
Sierks, Holger
Barbieri, Cesare
Lamy, Philippe
Rodrigo, Rafael
Koschny, Detlef
Rickman, Hans
Keller, Horst U.
Agarwal, Jessica
A’Hearn, Michael F.
Barucci, Maria A.
Bertaux, Jean-Loup
Boudreault, Steve
Cremonese, Gabriele
Deppo, Vania Da
Davidsson, Björn
Debei, Stefano
De Cecco, Mariolino
Deller, Jakob
Fornasier, Sonia
Fulle, Marco
Gicquel, Adeline
Groussin, Olivier
Gutierrez, Pedro J.
Güttler, Carsten
Hofmann, Marc
Höfner, Sebastian
Hviid, Stubbe F.
Ip, Wing-Huen
Jorda, Laurent
Knollenberg, Jörg
Kramm, J.-Rainer
Kührt, Ekkehard
Küppers, Michael
La Forgia, Fiorangela
Lara, Luisa M.
Lee, Jui-Chi
Lin, Zhong-Yi
Lopez Moreno, Jose J.
Marzari, Francesco
Michalik, Harald
Mottola, Stefano
Preusker, Frank
Scholten, Frank
Toth, Imre
Tubiana, Cecilia
Additional Credits
Journal
Astronomy and astrophysics
Publisher
EDP Sciences
ISSN
0004-6361
Access(Rights)
restricted
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