Dark Dune Spots: possible biomarkers on Mars?

Dark Dune Spots (DDSs) are transitional geomorphologic formations in the frost-covered polar regions of Mars. Our analysis of the transformations and arrangements of subsequent stages of DDSs into time sequence revealed their: (i) hole-like characteristics, (ii) development and formation from the bottom of the frosted layer till the disapperance of the latter, (iii) repeated (seasonal and annual) appearance in a pattern of multiple DDSs on the surface, and (iv) probable origin. We focused our studies on a model in which DDSs were interpreted as objects triggered by biological activity involved in the frosting and melting processes. We discuss two competing interpretations of DDSs: development by defrosting alone, and by defrosting and melting enhanced by the activity of Martian Surface Organisms (MSOs). MSOs are hypothetical Martian photosynthetic surface organisms thought to absorb sunlight. As a result they warm up by late winter and melt the ice around them, whereby their growth and reproduction become possible. The ice cover above the liquid water lens harbouring the MSOs provides excellent heat and UV insulation, prevents fast evaporation, and sustains basic living conditions until the ice cover exists. When the frost cover disappears MSOs go to a dormant, desiccated state. We propose further studies to be carried out by orbiters and landers travelling to Mars and by analysis of partial analogues on earth.