 | Otto K.A. Mass wasting and the Coriolis effect on asteroid Vesta: Diss. … Dr. rer. nat. / Deutsches Zentrum für Luft- und Raumfahrt, Institut für Planetenforschung, Berlin-Adlershof. - Köln: DLR, 2016. - xvii, 233,16 p.: ill., tab. - (Forschungsbericht; 2016-09). - Res. also Germ. - Bibliogr.: p.131-149. - ISSN 1434-8454 - ISSN 1434-8454
Шифр: (Pr 1120/2016-09) 02
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1 Introduction ............................................... 1
1.1 Motivation ................................................. 1
1.2 Outline .................................................... 2
2 The Main Asteroid Bel ...................................... 3
2.1 The Main Asteroid Belt at a Glance ......................... 3
2.2 Asteroid Spin and Impact Rates ............................. 7
2.3 The Dawn Mission ........................................... 9
2.3.1 Mission Objectives .................................. 9
2.3.2 Scientific Instruments ............................. 10
2.3.3 Mission Operations ................................. 12
2.4 Asteroid (4) Vesta ....................................... 13
2.4.1 The HED-Meteorites ................................. 15
2.4.2 Regolith ........................................... 16
2.4.3 Rheasilvia and Veneneia ............................ 17
2.4.4 Geology ............................................ 20
2.4.5 Shape and Gravity .................................. 25
3 Theoretical Background .................................... 27
3.1 Impact Cratering Dynamics ................................. 27
3.1.1 Contact and Compression Stage ...................... 27
3.1.2 Excavation Stage ................................... 29
3.1.3 Modification Stage ................................. 30
3.1.4 Crater Degradation ................................. 31
3.1.5 Acoustic Fluidisation .............................. 31
3.1.6 Acoustically Fluidised Material Properties ......... 33
3.1.7 The Rheasilvia Impact Event ........................ 35
3.2 The Coriolis Effect ....................................... 37
3.2.1 Forces in a Rotating Reference Frame ............... 37
3.2.2 Geodetic Reference Frame ........................... 39
3.2.3 Inertial Circles .................................. 40
3.2.4 Rossby Number ...................................... 43
4 Data ...................................................... 45
4.1 Digital Terrain Model ..................................... 45
4.2 Mosaic .................................................... 45
4.3 Map Projection ............................................ 47
5 Mass-Wasting Features within Rheasilvia ................... 49
5.1 Slumping ................................................. 49
5.2 Curved Ridges ............................................. 52
5.3 Coriolis Effect on Mass Movements ......................... 56
6 The Coriolis Model ........................................ 63
6.1 Aim ....................................................... 63
6.2 Mapping ................................................... 63
6.3 Computer-Based Analysis ................................... 66
6.3.1 Defining the Reference Frame ....................... 67
6.3.2 Calculating the Velocity ........................... 67
6.4 Ancient and Recent Vesta's Reference System ............... 70
6.5 Changing the Histogram's Bin Size ......................... 74
6.6 The Effect of Vesta's Topography .......................... 76
6.7 Error Analysis ............................................ 78
6.8 Data Illustration ........................................ 79
6.9 Deriving Acceleration and Slope ........................... 82
7 Results ................................................... 87
7.1 Region 1: 270°E to 360°E .................................. 89
7.1.1 Accelerating Velocity Sections ..................... 90
7.1.2 Decelerating Velocity Sections ..................... 94
7.1.3 Constant Velocity Sections ......................... 94
7.2 Region 2: The Rheasilvia and Veneneia Intersection ........ 98
7.2.1 Accelerating Velocity Sections ..................... 99
7.2.2 Decelerating Velocity Sections .................... 101
7.2.3 Constant Velocity Sections ........................ 101
7.3 Region 3: The Central Peak ............................... 102
7.3.1 Accelerating Velocity Sections .................... 103
7.3.2 Constant Velocity Sections ........................ 104
7.4 Material Properties ...................................... 105
7.4.1 Viscosity ......................................... 105
7.4.2 Coefficient of Friction ........................... 105
8 Discussion ............................................... 109
8.1 Region 1: 270°E to 360°E ................................ 109
8.2 Region 2: The Rheasilvia and Veneneia Intersection ....... 114
8.3 Region 3: The Central Peak ............................... 117
8.4 Material Properties ...................................... 119
8.4.1 Viscosity ......................................... 120
8.4.2 Coefficient of Friction ........................... 121
8.5 Dynamical Comparison of the Regions ...................... 123
8.6 Comparision to Other Mass-Wasting Velocities ............. 125
9 Conclusions and Summary .................................. 127
9.1 Conclusions .............................................. 127
9.2 Summary .................................................. 128
References ............................................... 131
Appendices ............................................... 153
A IDL-Code Samples ......................................... 154
A.l Calculating the Velocity ................................. 154
A 2 Ancient Vesta's Reference System ......................... 160
B Curve Plots and Statistics ............................... 163
B.l Curve Plots .............................................. 163
B.2 Curve Statistics ......................................... 196
B.3 Curve Measurements ....................................... 200
C Mass-Wasting Features and Processes in Vesta's South
Polar Basin Rheasilvia ................................... 233
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