Caves on Earth as proxies for Martian subsurface environments

On planet Earth, the inner part of cave systems represents an extreme and isolated environment, characterized by relatively stable microclimatic conditions, nutrient limitation and protection from external stressors such as radiation, wind and surface weathering. These features make them suitable analogues to Martian cave systems, which are identified as high-priority targets for astrobiological investigations. Microbial communities inhabiting Earth’s caves exhibit extremotolerant or extremophilic traits, offering valuable insights into potential microbial survival strategies on Mars. This mini-review explores the role of cave microbiomes as models for studying habitability, biosignature preservation and microbial adaptations relevant to Martian subsurface environments. We summarize recent findings on cave microbial diversity and their metabolic strategies, highlighting their implications for astrobiology. Additionally, we discuss how caves can function as biological time capsules, preserving biosignatures and microbial life relevant to future planetary exploration. We conclude that terrestrial caves offer key ecological and mineralogical analogs to Martian subsurface environments, and that microbial strategies observed in cave ecosystems such as chemolithotrophy, endolithic colonization and biofilm formation should be prioritized in designing future Mars life-detection missions.