Geophysical Exploration of Terrestrial and Lunar Volcanic Fields
Bell, Jr., Ernest Robert
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Planetary analogs are environments representative of current or past conditions on other planetary bodies. My research uses terrestrial volcanic fields as lunar analogs to conduct geophysical studies on the subsurface structure of cinder cones, lava flows, and lava tubes, as well as understand terrestrial field methods for application to lunar surface exploration. As part of this research, I relate the magnetic anomalies produced by lava tubes to their location and geomorphology. By comparison of magnetic anomalies against synthetic predictions, I derive a relationship between the terrestrial magnetic anomalies and underlying tube geometry. The model is shown to predict terrestrial lava tube magnetic anomalies, and adjusting for the lunar magnetic environment, anomalies resulting from tubes on the Moon. Active source seismic experiments performed by Apollo astronauts were used to determine lunar tectonic and volcanic structure at depth. Terrestrial geophysical analogs are useful for understanding the Apollo results, and for improving the quality of future lunar seismic studies. I use seismic refraction to attempt to identify subsurface continuation of locally mapped faults beneath lava flows and cinder deposits to examine their association to cinder cone vent chains. However, due to high seismic energy attenuation, my analysis was unable to resolve displacement of stratigraphic layers indicative of fault locations. The seismic attenuation properties of the field area were able to be characterized. I then analyze the Apollo 17 Lunar Seismic Profiling Experiment (LSPE) data and an Apollo LSPE equivalent terrestrial data set to provide insights into the subsurface imaging potential for a terrestrial equivalent array in the Taurus-Littrow Valley on the Moon. Finally, I insert active seismic refraction into a previously executed simulated human lunar rover mission where the traverse route and associated science station locations omitted geophysical studies. Data from these lines are used to create 1-D seismic velocity profiles to examine subsurface structural trends and geophysical features of the field area. The seismic fieldwork and analysis are related to similar activities performed by the Apollo 14 & 16 crews to highlight similarities in issues encountered with both terrestrial and lunar field operations, and discuss considerations for future human lunar surface science.