Magnetic and electromagnetic surveying of lava tubes at Lava Beds National Monument, California

Lava tubes are targets for future manned missions on Mars because they offer protection from ultraviolet radiation and meteor impacts. As a contribution to the Astrobiology Training in Lava Tubes project, this project aimed on the characterization and detection of lava tubes at Lava Beds National Monument (LBNM) using electromagnetic (EM) induction and magnetic techniques. Interior EM surveys were successful in characterizing cave floors with different conductivity signatures. The EM data was inverted in 1D to reveal structures in the basaltic bedrock. Forward modelling of magnetic showed that the signature associated with a lava tube is a magnetic low slightly offset from the axis of symmetry. Visual inspection of surface magnetic data did not identify this signature. Inversion of magnetic data showed good fit over the area of influence of a lava tube with one passage. Inversion also identified susceptibility and remanence signatures that could be related to eruption sequence.