Abstract

Lava tubes occupy a unique position in our ability to understand of the past, current, and future habitability of Mars. Shielded from radiation and micrometeorites, lava tubes represent environments where past extraterrestrial life may best be preserved and where present-day life in the subsurface may be most easily accessible. Into the future, crewed human missions to Mars may look to leverage lava tubes as natural shelters. Taken together, there is therefore a clear need to locate Martian lava tubes and understand their spatial extent.

The conventional way in which Martian lava tubes are identified is by searching for the overhanging shadows and/or diurnal thermal anomalies associated with skylights. However, it is difficult to estimate the full lateral extent of a buried cave system from skylights alone. To this end, spaceborne radar sounding measurements offer a unique surface penetrating capability that has long seemed a powerful, if so far unrealized, contribution to buried lava tube mapping efforts. In this study, we take a new approach inspired by radar sounding studies of features on the bed of the Antarctic Ice Sheet and look leverage the anticipated angular radar scattering extent of buried Martian lava tubes in order to assess their existence. Tested using 107 SHAllow RADar (SHARAD) orbits across the Western flank of Alba Mons, the results show promise in that anticipated radar-derived signals are preferentially observed close to previously interpreted lava tube structures. However, the ability to uniquely identify lava tubes is limited as similar angular radar scattering responses are also produced by other surface landforms such as ridges. Further work is required to refine the approach in other areas of Mars exhibiting less surface topography and the potential for “false” detection can be reduced.