Migrating and UV screening subsurface zone on Mars as target for the analysis of photosynthetic life and astrobiology

Analyzing the UV shielding capacity of two Mars simulant materials in laboratory (JSC-1 and basaltic sand), 1–2 mm thickness of these granular materials were enough to provide the required UV shielding for some extremophiles under Martian surface radiations, while light enough for photosynthesis could penetrate down to 4–5 mm depth. Between these two depth levels a PAR zone exists (photosynthetically active radiation between 400 and 700 nm that can be used by photosynthetic organism on Earth), where hypothetic organisms could photosynthesize in theory if other environmental parameters are tolerable. To identify the possible ideal locations we surveyed the spatial and temporal distribution of water ice on Mars inside this PAR zone at periods and locations where no CO2 ice is present on the surface.It was found that this PAR zone is filled with ice in the northern hemisphere of Mars for 31–35 Earth days for any certain location, and these locations form a receding ring-like zone there. Because of few observations and probably the small quantity of water ice there, the characteristics of such a ring could not be identifies for the southern hemisphere. The focused analysis of this ideal zone could be interesting in the future as based on theoretical reasons ephemeral liquid water as a thin film might appear there and give insight into the characteristics of astrobiological important locations on Mars.

► Shallow subsurface conditions were analyzed in laboratory inside Mars simulant sands.
► Two to four millimeter depth zone was found to be shielded from UV and provided enough light for photosynthesis.
► This zone at the northern hemisphere is filled with ice in spring for 2–6 days and dense vapour for 33–41 days.
► This migrating zone might be important for astrobiology and requires more focused analysis.