DETECTION AND CHARACTERIZATION OF LAVA TUBES FROM SURFACE SIGNATURES: TWO NEW APPROACHES

Abstract

Lava tubes are sinuous volcanic caves formed when a lava flow develops a solidified crust before draining out. On other planets and moons, lava tubes could be ideal sites for future exploration or habitation, providing practical and scientific benefits. Lava tubes are difficult to study without in-situ exploration, which is impossible for extraterrestrial, inaccessible, or filled tubes. We present two new techniques to constrain the internal morphologies of lava tubes, relying only on remotely observable surface features. Through modeling, we predict the surface features that lava tubes produce and quantify how the dimensions of these surface features depend on the dimensions of the tubes. Looking for these features in real data reveals several candidate tubes and allows us to constrain their dimensions. Large tubes on the Moon should cause tensile cracks in predictable patterns that reflect tube dimensions. Such cracks near discontinuities in Rimae Mairan, Sharp, and Marius indicate lava tubes with widths less than 2 km. Cracking inside lunar tubes would impair the usability of the floor for exploration, leaving less than 400 m of contiguous pristine floor in these three cases. Inflation ridges above tubes can also reveal tube morphologies. By modeling how Valentine Cave inflated, we constrain what conditions and age it must have had to produce the observed ridge. It and two similar examples must have inflated within the first 400 hours after roof formation. We build from this idea and discover a new, widely applicable relationship between the dimensions of an inflation ridge and the height, roof thickness, and width of its tube. From ridge topography alone, this relationship constrains a range of possible tube shapes. Searching for inflation ridges in a LiDAR dataset of the Lava Beds National Monument reveals eighteen candidate tubes. Most of these tubes share a similar range of possible shapes; one ridge shows a consistently different shape range, possibly indicating different formation conditions. Combined with constraints from other sources on two of these tubes, the shape ranges narrow to more specific results. These methods constitute two novel tools to find and study lava tubes on Earth and beyond.