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http://hdl.handle.net/20.500.12386/26109
Titolo: | The southern hemisphere of 67P/Churyumov-Gerasimenko: Analysis of the preperihelion size-frequency distribution of boulders ≥7 m | Autori: | PAJOLA, MAURIZIO LUCCHETTI, ALICE Vincent, Jean-Baptiste Oklay, Nilda El-Maarry, Mohamed R. 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 Da Deppo, Vania 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 Thomas, Nicholas Toth, Imre TUBIANA, Cecilia |
Data pubblicazione: | 2016 | Rivista: | ASTRONOMY & ASTROPHYSICS | Numero: | 592 | Da pagina:: | L2 | Abstract: | <BR /> 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. <BR /> 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°, 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. <BR /> 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 km<SUP>2</SUP> 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. | URI: | http://hdl.handle.net/20.500.12386/26109 | URL: | https://www.aanda.org/articles/aa/abs/2016/08/aa28887-16/aa28887-16.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/201628887 | Bibcode ADS: | 2016A&A...592L...2P | Fulltext: | open |
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