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Probing the Interior Structure of Venus Probing the Interior Structure of Venus Report by: Keck Institute for Space Studies (KISS) Venus Seismology Study Team April 1, 2015 Authors and Study Participants Name Institution Discipline E-mail Study Co-leaders David Stevenson Caltech Planetary geophysics [email protected] James Cutts JPL Mission analysis and space technology [email protected] David Mimoun ISAE/U-Toulouse Planetary instrumentation [email protected] Study Participants Stephen Arrowsmith Los Alamos National Lab Seismology, infrasonics [email protected] Bruce Banerdt JPL Geophysics—seismology [email protected] Philip Blom Los Alamos National Lab Infrasonics—postdoc [email protected] Emily Brageot JPL Infrared systems analysis—postdoc [email protected] Quentin Brissaud ISAE/Toulouse Systems analysis [email protected] Gordon Chin GSFC Venus, submillimeter spectroscopy [email protected] Peter Gao Caltech Planetary science, graduate student [email protected] Raphael Garcia ISAE/Toulouse Remote sensing of Venus seismic [email protected] events Jeffery Hall JPL Venus balloons, extreme environment [email protected] Gary Hunter NASA Glenn High-temperature sensors [email protected] Jennifer Jackson Caltech Geophysics, mineral physics [email protected] Viktor Kerzhanovich JPL (retired), former IKI Venus science, Venera missions [email protected] Walter Kiefer Lunar and Planetary Geophysics, planetary seismology [email protected] Institute Attila Komjathy JPL GPS sounding of Earth’s ionosphere [email protected] Christopher Lee Ashima Research Venus atmospheric science [email protected] Philippe Lognonné IPGP Univ, Paris Diderot Planetary geophysics [email protected] Ralph Lorenz APL Planetary science, Venus seismology [email protected] Walid Majid JPL Radio astronomy, planetary science [email protected] Mohammed Mojarradi JPL High-temperature electronics [email protected] Guust Nolet University of Nice Seismology, hydroacoustics [email protected] Joseph O’Rourke Caltech Planetary science—graduate student [email protected] Lucie Rolland Los Alamos National Lab Ionosphere seismology [email protected] Gerald Shubert UCLA Geophysics, interiors and atmospheres [email protected] Mark Simons Caltech Geophysics [email protected] Christophe Sotin JPL Venus thermal and tectonic history [email protected] Tom Spilker Consultant Planetary mission design, seismology [email protected] Victor Tsai Caltech Geophysics—seismology [email protected] Acknowledgments We would like to thank members of the study team for their contributions to this report during the initial teleconferences, at the workshop itself, and in the preparation of the report. Without the diverse talents and enthusiasm of our study team, this report never could have happened. On behalf of members of the study team, we would like to thank Michelle Judd, Managing Director of the Keck Institute for Space Studies, for her role in creating the collaborative environment that was so vital to the success of our study. We would also like to thank Prof. Tom Prince, Director of the Keck Institute for Space Studies, for his guidance and the KISS Steering Committee for the confidence they placed in our team by selecting our study for funding. In the preparation of this report, we would like to acknowledge Samantha Ozyildirim of JPL for her thorough review and editing and layout of the report. Corby Waste, also of JPL, was responsible for creating the cover art. Dr. Suzanne Smrekar provided insightful comments. We acknowledge NASA’s Jet Propulsion Laboratory and the California Institute of Technology for their support of the study and for making it possible for key study participants to be involved. Finally, we would like to thank the W.M. Keck Foundation for their foresight in establishing the Keck Institute for Space Studies and the new facilities, which were so conducive to the workshop process. James A. Cutts David Mimoun David J. Stevenson Co-leads of the KISS study on Venus Seismology Table of Contents Executive Summary ....................................................................................................................................................... 1 1 Introduction ............................................................................................................................................................. 4 2 Science ................................................................................................................................................................... 5 2.1 Venus—its Atmosphere, Surface, and Interior ............................................................................................. 5 2.2 The Importance of Venus ............................................................................................................................. 7 2.3 The Scientific Case for Venus Seismology .................................................................................................. 8 3 Seismic Sources on Venus ..................................................................................................................................... 9 3.1 Venus Quakes .............................................................................................................................................. 9 3.1.1 Active Faulting ................................................................................................................................. 9 3.1.2 Seismic or Aseismic Strain Relief .................................................................................................. 10 3.1.3 Estimates of Seismic Activity ......................................................................................................... 10 3.2 Volcanic Activity ......................................................................................................................................... 11 3.3 Impacting Bolides ....................................................................................................................................... 11 3.4 Atmospheric Sources ................................................................................................................................. 11 3.5 Artificial Sources ........................................................................................................................................ 12 3.5.1 Airburst vs. Ground Source ........................................................................................................... 12 3.5.2 Chemical vs. Phase Change Explosive Sources ........................................................................... 13 3.5.3 Discussion ..................................................................................................................................... 13 4 Seismology Techniques ........................................................................................................................................ 14 4.1 Historical Perspective ................................................................................................................................. 14 4.2 Seismology Basics ..................................................................................................................................... 15 4.2.1 Classical Seismology ..................................................................................................................... 15 4.2.2 Propagation of the Seismic Waves in the Atmosphere .................................................................. 16 4.2.3 A ‘Generalized’ Seismology Approach........................................................................................... 18 4.3 Surface, Middle Atmosphere, and Space Vantage Points.......................................................................... 19 5 Seismology on the Venus Surface ........................................................................................................................ 20 5.1 Prior Planetary Surface Seismic Experiments ............................................................................................ 20 5.1.1 Lunar—Apollo Lunar Seismic Experiments ................................................................................... 20 5.1.2 Mars—Viking 1 and 2 .................................................................................................................... 20 5.1.3 Venus—Venera 13 and 14 ............................................................................................................ 21 5.1.4 Mars—InSight Seismic Interior Structure Experiment .................................................................... 22 5.2 Key Constraints for a Seismic Experiment on the Surface of Venus .......................................................... 23 5.3 Performance Requirements ....................................................................................................................... 23 5.4 Seismic Backgrounds on the Venus Surface ............................................................................................. 24 5.4.1 Natural Environment ...................................................................................................................... 25 5.4.2 Spacecraft (Anthropogenic) Effects ............................................................................................... 25 5.5 Technology Status ....................................................................................................................................
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