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

    Pajola, M. and Lucchetti, A. and Vincent, J.-B. and Oklay, N. and El-Maarry, Mohamed Ramy and Bertini, I. and Naletto, G. and Lazzarin, M. and Massironi, M. and Sierks, H. and Barbieri, C. and Lamy, P. and Rodrigo, R. and Koschny, D. and Rickman, H. and Keller, H. U. and Agarwal, J. and A’Hearn, M.F. and Barucci, M.A. and Bertaux, J.-L. and Boudreault, S. and Cremonese, G. and Deppo, V.D. and Davidsson, B. and Debei, S. and De Cecco, M. and Deller, J. and Fornasier, S. and Fulle, M. and Gicquel, A. and Groussin, O. and Gutierrez, P.J. and Güttler, C. and Hofmann, M. and Höfner, S. and Hviid, S.F. and Ip, W.-H. and Jorda, L. and Knollenberg, J. and Kramm, J.-R. and Kührt, E. and Küppers, M. and La Forgia, F. and Lara, L.M. and Lee, J.-C. and Lin, Z.-Y. and Lopez Moreno, J. J. and Marzari, F. and Michalik, H. and Mottola, S. and Preusker, F. and Scholten, F. and Thomas, N. and Toth, I. and Tubiana, C. (2016) The southern hemisphere of 67P/Churyumov-Gerasimenko: Analysis of the preperihelion size-frequency distribution of boulders ≥7 m. Astronomy & Astrophysics 592 , L2. ISSN 0004-6361.

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    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°, 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.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): comets: general / comets: individual: 67P/Churyumov-Gerasimenko / methods: data analysis
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: Administrator
    Date Deposited: 26 Oct 2018 11:44
    Last Modified: 26 Oct 2018 11:44
    URI: http://eprints.bbk.ac.uk/id/eprint/24835

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