The Feasibility of In-Situ Observations of Europa's Water Vapour Plumes
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The feasibility of in-situ observations of Europa's water vapour plumes H.L.F. HUYBRIGHS DELFT UNIVERSITY OF TECHNOLOGY SWEDISH INSTITUTE OF SPACE PHYSICS April 2015 Cover page: JUICE spacecraft from: http://sci.esa.int/juice/48350-juice-spacecraft/, Europa model from: http://photojournal.jpl.nasa.gov/catalog/PIA01130. 1 of 110 MASTER’S THESIS SUPERVISORS (HANS) H.L.F. HUYBRIGHS – 1542567 PROF. DR. S. BARABASH (IRF) [email protected] DR. Y. FUTAANA (IRF) [email protected] PROF. DR. L.L.A. VERMEERSEN (TU DELFT) The feasibility of in-situ observations of Europa’s water vapour plumes 2 of 110 ACKNOWLEDGEMENTS First and foremost, I wish to thank my supervisors Dr. Yoshifumi Futaana and Prof. Stas Barabash at IRF and Prof. Bert Vermeersen at Tu Delft, for supporting this exciting Master’s thesis project. Special thanks go to Dr. Yoshifumi Futaana for countless valuable discussions and teachings by the drawing board. Thanks go to all my friends and colleagues at IRF for advice and support, I won’t list you all in case I forget someone. Special thanks go to Charles Lue and Jesper Lindkvist for helping me out regularly with many different aspects of space physics and numerical simulations. Gratitude also goes to Dr. Lorenz Roth (Kungliga Tekniska Högskolan, Stockholm) for giving some valuable feedback on the plume model; and to Prof. Peter Wurz (University of Bern) and Dr. Martin Wieser (IRF) for providing information on the performance of NIM and JDC. I would also like to thank my family and friends back home, for having to miss me during my stay in the North. This Master’s thesis project has been partially funded by the European Commission’s Erasmus+ project. 3 of 110 TABLE OF CONTENTS Acknowledgements ..........................................................................................................................................................................3 List of acronyms .................................................................................................................................................................................8 Summary ............................................................................................................................................................................................. 10 1 Overview ................................................................................................................................................................................... 12 2 Introduction ............................................................................................................................................................................ 14 2.1 Europa as a planetary body................................................................................................................................... 14 2.1.1 Europa tidal heating and stress ................................................................................................................ 14 2.1.2 Interior and oceans ......................................................................................................................................... 15 2.1.3 Geology .................................................................................................................................................................. 16 2.1.4 Surface composition ....................................................................................................................................... 17 2.1.5 Exosphere ............................................................................................................................................................. 18 2.1.5.1 Exosphere composition ........................................................................................................................... 18 2.1.5.2 Ionosphere ...................................................................................................................................................... 19 2.1.5.3 Neutral torus ................................................................................................................................................. 19 2.1.6 Europa as a potentially habitable moon ............................................................................................... 20 2.2 Europa’s magnetospheric environment ......................................................................................................... 21 2.2.1 General overview of Jupiter’s magnetosphere .................................................................................. 21 2.2.2 Europa’s magnetic, plasma and energetic particle environment ............................................ 23 2.3 Europa’s interaction with Jupiter’s magnetosphere ................................................................................ 25 2.3.1 Interaction, upstream perspective .......................................................................................................... 25 2.3.2 Interaction, Europa perspective ............................................................................................................... 25 2.3.3 Interaction, downstream perspective ................................................................................................... 27 2.4 Europa’s water vapour plumes ........................................................................................................................... 28 2.4.1 Discovery of the water vapour plumes ................................................................................................. 28 2.4.2 Findings since the first discovery of the water vapour plumes ............................................... 29 2.4.3 Existence of plumes suggested in literature ...................................................................................... 30 2.4.4 Previous unsuccessful observations ...................................................................................................... 31 2.4.5 Conclusion and open questions ................................................................................................................ 31 2.5 JUICE Europa flybys overview ............................................................................................................................. 32 2.6 PEP: Particle Environment Package on-board JUICE............................................................................... 34 2.6.1 Jovian plasma Dynamics and Composition analyser (JDC) ........................................................ 35 The feasibility of in-situ observations of Europa’s water vapour plumes 4 of 110 2.6.2 Neutral gas and Ions Mass spectrometer (NIM) .............................................................................. 37 3 Project plan, research questions and method ....................................................................................................... 40 3.1 Research question, research objectives and sub-goals........................................................................... 40 3.2 Theoretical content and methodology ............................................................................................................ 41 4 Neutral plume particle simulations ............................................................................................................................ 44 4.1 Method ............................................................................................................................................................................. 44 4.1.1 Overview of the model................................................................................................................................... 44 4.1.2 Plume source model ....................................................................................................................................... 45 4.1.3 Non-collisional ................................................................................................................................................... 46 4.1.4 Superparticles .................................................................................................................................................... 46 4.1.5 Particle trajectories ......................................................................................................................................... 46 4.1.6 Leap frog integration ...................................................................................................................................... 47 4.1.7 From trajectories to density ....................................................................................................................... 47 4.1.8 Not generating new particles at each time step ............................................................................... 48 4.1.9 From density to NIM count rate ............................................................................................................... 48 4.2 Simulation inputs – plume model ...................................................................................................................... 49 4.3 Simulation inputs – grid properties .................................................................................................................. 50 4.4 Results .............................................................................................................................................................................. 52 4.4.1 Density