Potential caves on Mars: From orbital evidence to subsurface exploration

Potential caves on Mars are scientifically important targets because they may preserve geological, volatile and environmental records while providing sheltered subsurface settings relevant to astrobiological investigation and future robotic exploration. This review synthesizes current orbital and geophysical evidence for Martian potential caves to evaluate how candidate entrances can be identified, how their geological origins can be interpreted, and what observations are required to establish subsurface connectivity. We assess morphological, thermophysical, topographic, compositional and radar observations according to the physical properties they measure, their spatial scales and acquisition geometries, and their ability to distinguish cave-related interpretations from plausible alternatives. We further separate candidate cave entrances from potential caves supported by convergent observations, distinguish morphological classification from geological origin, and evaluate volcanic, tectonic, water-modified and ice-related settings while emphasizing that current MARSIS and SHARAD observations primarily constrain regional subsurface structure rather than directly detect individual caves. The synthesis shows that recessed geometry, repeatable shadow behaviour, compatible thermophysical responses and geological context can collectively strengthen a potential-cave interpretation, but no single orbital observable uniquely demonstrates an entrance-connected subsurface cavity. Future progress therefore requires higher-resolution and repeat orbital observations, targeted local geophysical measurements and robotic reconnaissance, with definitive confirmation ultimately depending on direct in situ observation and three-dimensional mapping of an entrance-connected interior.