The search for life on Mars has been intimately linked to the identification of unequivocal ancient or modern geomarkers [9, 10] of water (e.g. some water-related minerals) on and inside the planet. Recently, some water-related sulfates (e.g. jarosite, gypsum) were discovered [11-13] on Mars surface. In particular, jarosite has proven to have a great astrobiological importance, not only for its relation with liquid water, but also because it can act as a sink and source of Fe ions for Fe-related chemolithoautotrophic microorganisms, such as those encountered in numerous extremophilic ecosystems (e.g. Tinto river [14-16]). In the present report, we present experimental results on the UV shielding capabilities of the above mentioned minerals: jarosite (KFe3(SO4)2(OH)6) and gypsum (CaSO4.2H2O).
The samples of jarosite and gypsum used in this work come from two selected areas of the SE Mediterranean region of Spain: Jaroso and Sorbas, which have been proposed as a relevant geodynamic and mineralogical model [17-21] to follow for the astrobiological exploration of Mars. The Jaroso Hydrothermal System is a volcanism-related multistage hydrothermal episode of Upper Miocene age, which includes oxy-hydroxides (e.g. hematite), base-and precious-metal sulfides and different types of sulphosalts. Hydrothermal sulfuric acid weathering of the ores has generated huge amounts of oxide and sulfate minerals [19, 22-24] of which jarosite is the most abundant. It is important to note that jarosite was first discovered on Earth at this area, in 1852, in the “Jaroso Ravine”, which is the world type locality of jarosite [25, 26]. The Sorbas basin contains one of the most complete sedimentary successions of the Mediterranean (gypsum karst) reflecting the increasing salinity during the Messinian salinity crisis (desiccation of the Mediterranean Sea) [27-29] and showing a complex paleogeographical evolution, being a signature of its progressive restriction and isolation.