Detection and characterization of the Naturalistas and Tahiche lava tubes (Lanzarote, Canary Islands) using vector fluxgate and scalar magnetometer measurements

Lava tubes and other subsurface cavities represent key targets for planetary exploration, as they could provide shelter from radiation for astronauts during future exploration missions and are high-priority astrobiology sites. While these structures have been identified on Mars and the Moon, characterization requires conducting geophysical surveys that may first be proven on terrestrial analogs. Among available geophysical methods, magnetic surveys using aerial platforms (e.g., drones or helicopters) offer a cost-effective and easily deployed approach.

The island of Lanzarote (Canary Islands, Spain) is renowned for its volcanic structures—including volcanoes, calderas, and lava tubes—similar to those found on other planetary bodies, particularly Mars. In May 2023, the NASA Goddard Instrument Field Team acquired vector fluxgate and scalar magnetic measurements over three lava tubes in Lanzarote: La Corona, Los Naturalistas, and Tahiche. Previous analyses of the data collected over the Corona lava tube demonstrated the feasibility of using fluxgate magnetic measurements to detect and characterize subsurface cavities. This study focuses on the Naturalistas and Tahiche tubes, which are significantly shallower, shorter, and narrower than La Corona. Specifically, Tahiche exhibits a complex geometry with abrupt changes in size and trajectory. These varied tube geometries provide complementary case studies for validating magnetic surveys for cavity detection, a critical step before conducting magnetometer surveys on other planetary bodies.

We processed our measurements and calculated magnetic anomalies of both the total magnetic field and each of the fluxgate Cartesian vector components. We also applied several enhancement techniques to constrain the location, size, and depth of the two lava tubes. Lastly, we built 2D magnetic forward models for each magnetic transect to reconstruct the geometry and trajectory of the Naturalistas and Tahiche tubes using magnetic data alone. Those geometries will be compared with LiDAR data collected from the tube interiors during the same field campaign. These results provide important guidelines for designing future magnetic surveys on the surfaces of Mars and Moon.