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Masterarbeit / Master's Thesis MASTERARBEIT / MASTER’S THESIS Titel der Masterarbeit / Title of the Master‘s Thesis „Polygonal Impact Craters (PICs) on Rhea, Dione, Tethys, Ceres and Vesta“ verfasst von / submitted by Tanja Neidhart, BSc angestrebter akademischer Grad / in partial fulfilment of the requirements for the degree of Master of Science (MSc) Wien, 2018 / Vienna 2018 Studienkennzahl lt. Studienblatt / A 066 861 degree programme code as it appears on the student record sheet: Studienrichtung lt. Studienblatt / Astronomie degree programme as it appears on the student record sheet: Betreut von / Supervisor: Univ.-Prof. Dr. Maria Gertrude Firneis Contents Acknowledgements I List of Abbreviations IX 1 Introduction 1 1.1 Definition of a Polygonal Impact Crater (PIC) . 1 1.2 Overview ......................................... 2 1.3 Formation of Polygonal Impact Craters (PICs) . 3 2 Previous studies on Polygonal Impact Craters (PICs) 9 2.1 PICsonMercury..................................... 9 2.2 PICsonVenus ....................................... 12 2.3 PICsontheMoon ...................................... 15 2.4 PICsonMars......................................... 20 2.5 PICs on other Solar System bodies . 23 3 Data and Methods 29 4 Saturnian Satellites 33 4.1 Rhea............................................. 33 4.2 Dione ............................................. 35 4.3 Tethys........................................... 38 5 Asteroid Belt Objects 43 5.1 Ceres............................................ 43 5.2 Vesta............................................ 46 6 Studies of Polygonal Impact Craters (PICs) on Saturnian Satellites 53 6.1 PICsonRhea........................................ 53 6.2 PICsonDione ........................................ 60 6.3 PICsonTethys...................................... 67 7 Studies of Polygonal Impact Craters (PICs) on Asteroid Belt Objects 73 7.1 PICsonCeres....................................... 73 7.2 PICsonVesta....................................... 80 8 Discussion 87 9 Conclusion 91 Abstract in English 93 Abstract in German 95 Acknowledgements First of all, I would like to express my gratitude to my supervisor Univ.-Prof. Dr. Maria Firneis (Institute of Astrophysics, University of Vienna) for her continuous support and motivation during the time I worked on this thesis. Further, I would like to thank Dr. Johannes Leitner (Research Platform: ExoLife, University of Vienna) for his advice, patient guidance, and endless discussions on the topic of this thesis and sci- ence in general. Special thanks are also due to Florian Hofbauer, BSc (Institute of Pathology, Karl Landsteiner University, Krems) for his patience while helping me with the installation of ISIS 3. I owe my deepest gratitude to my parents, for their continual support and encouragement. They have enabled me to pursue all my interests and always believed in me. Finally, I would also like to give thanks to my family and friends for their support during my work on this thesis and for my life in general. I II List of Figures 1.1 Examples of PICs on several bodies of the Solar System . 1 1.2 PICs north of the Argyre basin, Mars . 2 1.3 Barringer Crater, Arizona . 4 1.4 Models of PIC formation . 6 1.5 Simple-to-complex transition diameter . 7 2.6 Impact crater Saikaku on Mercury . 10 2.7 Number of straight rims on Mercury . 10 2.8 Distribution of diameters of ICs and PICs on Mercury . 11 2.9 Distribution of ICs and PICs on Mercury . 11 2.10 PIC Abigail on Venus . 12 2.11 Distribution of ICs and PICs on Venus’ surface . 13 2.12 Diameters of non-polygonal impact craters and PICs on Venus . 13 2.13 Relation between orientation of straight rim segments and Corona . 14 2.14 Mean relative age of geological units and PICs on Venus . 15 2.15 PICs Kepler and Timocharis on the Moon . 17 2.16 Study region of PICs on the Moon . 18 2.17 Diameters of non-polygonal impact craters and PICs on the Moon . 19 2.18 Study regions of PICs on Mars . 20 2.19 PICs north of the Argyre basin, Mars . 21 2.20 PICs in the Argyre region, Mars . 21 2.21 Distribution of diameters of ICs and PICs in the Argyre region, Mars . 22 2.22 Relation between straight rims and fractures on Mars . 23 2.23 Distribution of PICs on the surface of Ceres . 24 2.24 Number of edges of PICs on Ceres . 24 2.25 Dione’s wispy and non-wispy terrain . 25 2.26 Study regions of PICs on Dione . 25 2.27 Map of faults on Dione . 26 2.28 Distribution of diameters of ICs and PICs in Dione’s non-wispy terrain . 27 3.29 IAU/NASA/USGS Planetary Database, Craters on Tethys . 29 3.30 Surface of Ceres ISIS 3 “qview” . 30 3.31PICMeanderionCeres ................................. 31 3.32PICLepidaonVesta................................... 31 4.33 Rhea’strailinghemisphere. 33 4.34 Impact craters on Rhea’s surface . 35 4.35 Bright stripes on Rhea’s surface . 35 4.36 Image of Dione taken by Cassini . 36 4.37 Surface of Dione . 37 4.38 Impact crater Creusa on Dione . 38 4.39 Impact basin Odysseus on Tethys . 39 4.40 Ithaca Chasma on Tethys . 40 4.41 Temperature variations on Mimas and Tethys . 41 5.42 Image of Ceres taken by Dawn . 43 5.43 Heavily cratered surface of Ceres . 45 5.44 Occator crater on Ceres . 46 5.45 Ahuna Mons on Ceres . 46 5.46 Image of Vesta taken by Dawn . 47 5.47 Impact craters Numisia and Cornelia on Vesta . 48 5.48SurfaceofVesta..................................... 49 5.49 Impact basins on Vesta’s southern hemisphere . 50 5.50 Topographic profile of Rheasilvia basin on Vesta . 50 6.51 PIC Agunua on Rhea . 53 6.52 Number of straight rims on Rhea . 55 III 6.53 Distribution of diameters of impact craters on Rhea . 57 6.54 Distribution of diameters of ICs and PICs on Rhea . 57 6.55 Distribution of ICs and PICs on Rhea . 58 6.56 Distribution of ICs and PICs on the north and south poles of Rhea . 58 6.57 Distribution of ICs and PICs in the equatorial region of Rhea . 59 6.58 Number of straight rims as a function of crater size on Rhea . 59 6.59 PICs and non-polygonal impact craters on Rhea’s surface . 60 6.60 PIC Assaracus on Dione . 60 6.61 Number of straight rims on Dione . 62 6.62 Distribution of diameters of impact craters on Dione . 63 6.63 Distribution of diameters of ICs and PICs on Dione . 63 6.64 Distribution of ICs and PICs on Dione . 64 6.65 Distribution of ICs and PICs on the north and south poles of Dione . 64 6.66 Distribution of ICs and PICs in the equatorial region of Dione . 65 6.67 Number of straight rims as a function of crater size on Dione . 65 6.68 PICs and non-polygonal impact craters on Dione’s surface . 66 6.69PICIcariusonTethys ................................. 67 6.70 Number of straight rims on Tethys . 68 6.71 Distribution of diameters of impact craters on Tethys . 69 6.72 Distribution of diameters of ICs and PICs on Tethys . 70 6.73 Distribution of ICs and PICs on Tethys . 70 6.74 Distribution of ICs and PICs on the north and south poles of Tethys . 71 6.75 Distribution of ICs and PICs in the equatorial region of Tethys . 71 6.76 Number of straight rims as a function of crater size on Tethys . 72 6.77 PICs and non-polygonal impact craters on Tethys’ surface . 72 7.78PICFejokooonCeres .................................. 73 7.79 Number of straight rims on Ceres . 75 7.80 Distribution of diameters of impact craters on Ceres . 76 7.81 Distribution of diameters of ICs and PICs on Ceres . 77 7.82 Distribution of ICs and PICs on Ceres . 77 7.83 Distribution of ICs and PICs on Ceres’ surface . 78 7.84 Number of straight rims as a function of crater size on Ceres . 78 7.85 PICs and non-polygonal impact craters on Ceres’ surface . 79 7.86PICCanuleiaonVesta................................. 80 7.87 Number of straight rims on Vesta . 82 7.88 Distribution of diameters of impact craters on Vesta . 83 7.89 Distribution of diameters of ICs and PICs on Vesta . 83 7.90 Distribution of ICs and PICs on Vesta . 84 7.91 Distribution of ICs and PICs on Vesta’s surface . 84 7.92 Number of straight rims as a function of crater size on Vesta . 85 7.93 PICs and non-polygonal impact craters on Vesta’s surface . 85 8.94 Number of straight rims of Rhea, Dione, Tethys, Ceres, and Vesta . 87 IV Ich habe mich bemuht,¨ samtliche¨ Inhaber der Bildrechte ausfindig zu machen, und ihre Zustimmung zur Verwendung der Bilder in dieser Arbeit eingeholt. Sollte dennoch eine Urheberrechtsverletzung bekannt werden, ersuche ich um Meldung bei mir. V VI List of Tables 3.1 Diameters of impact craters and resolution of maps . 30 6.2 FoundPICsonRhea.................................... 55 6.3 Measured diameters for impact craters on Rhea . 56 6.4 FoundPICsonDione .................................... 61 6.5 FoundPICsonTethys .................................. 67 7.6 FoundPICsonCeres................................... 75 7.7 FoundPICsonVesta................................... 81 8.8 Percentage of PICs, mean number of straight rims and angles . 87 8.9 Percentage of PICs, mean angle on Mercury, Venus, Mars, the Moon and the objects of this study (Rhea, Dione, Tethys, Ceres, Vesta) . ..
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