Mars's Subsurface: The Real Frontier in the Search for Life
Mars’s surface is harsh today, so if life ever existed it may have retreated underground to environments from metres to kilometres deep where rock, ice, and radiolytic chemistry could provide energy. While some models and Earth analogues suggest plausible habitats, there is no direct evidence of life beneath Mars; current samples reach only a few centimetres, and the envisioned deeper habitats—potentially many kilometres down—remain unprobed. The upcoming Rosalind Franklin/ExoMars drill could sample to about two metres, but confirming deep underground life would require access far deeper than any mission yet attempted.
