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The question about the stability of certain biomolecules is directly connected to the life-detection missions aiming to search for past or present life beyond Earth. The extreme conditions experienced on extraterrestrial planet surface (e.g. Mars), characterized by ionizing and non-ionizing radiation, CO2-atmosphere and reactive species, may destroy the hypothetical traces of life. In this context, the study of the biomolecules behaviour after ionizing radiation exposure could provide support for the onboard instrumentation and data interpretation of the life exploration missions on other planets. Here, as a part of STARLIFE campaign, we investigated the effects of gamma rays on two classes of fungal biomolecules–nucleic acids and melanin pigments – considered as promising biosignatures to search for during the ‘in situ life-detection’ missions beyond Earth.

BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports—among others—the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit., This research was supported by the Italian Space Agency (ASI grant BIOMEX Cyano 051-R.0 to D.B., ASI grant BIOMEX MicroColonial Fungi 063-R.0 to S.O.); the German Aerospace Center (DLR-grants: Department of Infrastructure and Management, Astrobiology Laboratories through a grant DLR-FuW-Project BIOMEX (2474128)/ Department of Radiation Biology supported by the grant DLR-FuE-Projekt ISS LIFE, Programm RF-FuW, Teilprogramm 475); the German Helmholtz Association through the Helmholtz-Alliance ‘‘Planetary Evolution and Life’’; the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, project SUBLIMAS ‘‘SUrvival of Bacteria and LIchens on Mars Analogs and Space,’’ ESP2015- 69810-R, 2015, to R. de la Torre, and project ‘‘CTM2015- 64728-C2-1-R’’ to L.G. Sancho); and the National Academy of Sciences of Ukraine (grant 47/2017).

The next two rover missions to Mars, ESA/Roscosmos’s ExoMars2020 and NASA’s Mars2020, will carry for the first time Raman spectrometers potentially able to dectect traces of past or present life. To support and interpret future spectroscopic data correctly a better understanding of potential habitable environments and putative biosignatures, using analogue environments such as the Atacama Desert, is of paramount importance. In the Atacama Desert, one of the driest places on Earth, life has developed adaptive strategies to decreasing amounts of water: from refuges inside or below rocks as endoliths or hypoliths to inside salts in hygroscopic niches (Davila & Schulze-Makuch, 2016). In the hyperarid core one of the last refuges for life are inside salt crusts using deliquescence as a water source or being in the subsurface waiting for transitory episodes of increased moisture (Schulze-Makuch et al., 2018). These adaptive strategies might also apply to putative Martian life which endured a transition from a water rich past to the very harsh surface conditions of the present giving us clues on where to best look for traces of life on the Red Planet. Salt crusts and salt nodules are particularly interesting targets in this regard because they reside on or very near the surface and are thus easily accessible to future robotic missions. In the Atacama, salt nodules have been shown to host photosynthetic organisms containing easily identifiable pigments by Raman spectroscopy such as carotenoids and scytonemin (Vítek et al., 2014). One of the most damaging factors for life and its remains, both in the Atacama and on Mars, is solar radiation. To investigate the spatial distribution of potential Raman signatures in micro-niches we generated georeferenced 3D-reconstructions of the sampling areas using photogrammetry techniques and plotted the dose received according to the nodules’ orientation. We then analysed salt nodule along dry cut north-south thick sections using Raman mapping to infer any relations between the amount of light received and the presence of detectable signal. Preliminary data show an increased presence of carotenoids, scytonemin, and other biomolecules signals on the nodules oriented towards the south, which are the-more-protected sections of the nodules. References Davila, A.F. & Schulze-Makuch, D. (2016) The Last Possible Outposts for Life on Mars. Astrobiology 16:159–168. Schulze-Makuch, D., Wagner, D., Kounaves, S.P., Mangelsdorf, K., Devine, K.G., Vera, J.-P. de, Schmitt-Kopplin, P., Grossart, H.-P., Parro, V., Kaupenjohann, M., Galy, A., Schneider, B., Airo, A., Frösler, J., Davila, A.F., Arens, F.L., Cáceres, L., Cornejo, F.S., Carrizo, D., Dartnell, L., DiRuggiero, J., Flury, M., Ganzert, L., Gessner, M.O., Grathwohl, P., Guan, L., Heinz, J., Hess, M., Keppler, F., Maus, D., McKay, C.P., Meckenstock, R.U., Montgomery, W., Oberlin, E.A., Probst, A.J., Sáenz, J.S., Sattler, T., Schirmack, J., Sephton, M.A., Schloter, M., Uhl, J., Valenzuela, B., Vestergaard, G., Wörmer, L. & Zamorano, P. (2018) Transitory microbial habitat in the hyperarid Atacama Desert. PNAS 115:2670–2675. Vítek, P., Jehlička, J., Ascaso, C., Mašek, V., Gómez-Silva, B., Olivares, H. & Wierzchos, J. (2014) Distribution of scytonemin in endolithic microbial communities from halite crusts in the hyperarid zone of the Atacama Desert, Chile. FEMS Microbiology Ecology 90:351–366.

Cryptoendolithic microbial communities, discovered in the extremely cold, hyper-arid McMurdo Dry Valleys of Antarctica (Friedmann 1982), the most similar terrestrial environments to Mars surface (Wynn-Williams and Edwards 2000; Onofri et al., 2004), have been considered as a candidate in supporting the search of life in Mars exploration. In such harsh conditions, microorganisms grow in airspaces among mineral grains and show some adaptations, as the accumulation of protective pigments and compatible solutes, assuring their survival. In the frame of the Lichen and Fungi experiment (LIFE, P.I. Silvano Onofri; Onofri et al. 2012, 2015), small samples of these communities, were exposed to space, in the EXPOSE-E facility for 1.5 years, with an exposition to vacuum (10-7 to 10-4 Pa) (Horneck et al., 2010), galactic cosmic radiation (≤190mGy) (Berger et al., 2012), and the full spectrum of solar extraterrestrial electromagnetic radiation to which cryptoendolithic microorganisms demonstrated to survive (Scalzi et al., 2012). The search for trace of extant or extinct life is one of the main goals of the future space mission beyond Earth. The future rover missions ExoMars 2020 (ESA-Roscomos) and Mars 2020 (NASA) are exploring chemical and biological indicators of life, called biomarkers. A good biomarker must have a biogenic origin and thus must unequivocally be identified as possible trace of life. The detection of biomarkers on Mars was the aim of BIOMEX (BIOlogy and Mars Experiment) project, in which has been investigated the alteration of different biomarkers, after exposure to space and Mars-like conditions outside the International Space Station. In this contest, the aim of this work was to characterize fungal biomarkers from these exposed rock samples, with different approaches: i) Raman spectroscopy and InfraRed analyses, which has been considered excellent tools for the detection of inorganic and organic molecules, such as microbial pigments and ii) -omics approaches, as lipidomic and metabolomic techniques, performed to detect biological macromolecules and to determine their stability after space exposure. The focus of lipidomics and metabolomics has been on biomarker discovery, with the aim of identifying metabolites that are correlated with environmental exposures. The results suggest that microbial molecules can be detected through different techniques. In particular, our attention was focused on pigments, such as melanin and carotenoids that maintain their stability also after 1.5 years of space exposure. These results are of importance for the upcoming life-detection missions on Mars finalized for the search for past, extant or extinct life outside the Earth.

Mars and the Jovian and Saturnian moons (Europa and Enceladus) are the next targets to search for life in our Solar System. New life detection instruments are indeed ready to be sent to Mars in 2020 (onboard ESA/Roscomos’s ExoMars2020 and NASA’s Mars2020 rovers) and possibly further. Among them, spectroscopy methods such as Raman or infrared are promising techniques that can give insights on both the mineralogical context and the identification of biosignatures. However, to support and interpret spectroscopic data correctly, as well as to guide future life detection missions, a better understanding of possibly habitable environments and potentially detectable biosignatures is of paramount importance. During the last years extensive field and laboratory investigations focused on demonstrating the capabilities of such technologies to characterize both mineral and biological samples of relevance to Mars but very few assessed potential biosignatures degradation under Mars-like or space-like conditions. To this end we are using samples from ground-based and space exposure experiments, the STARLIFE [1] and the BIOMEX [2] projects, to characterize their Raman and IR signatures after space and Mars relevant stresses. BIOMEX was part of the EXPOSE-R2 mission of the European Space Agency, which allowed a 15-month exposure on the outer side of the International Space Station and STARLIFE is an international campaign to study the role of galactic cosmic radiation in astrobiological systems. A wide range of extremophilic organisms such as cyanobacteria, permafrost green-algae, iron bacteria or methanogens and selected biomolecules exposed under these conditions will help us to define targets for future missions to Mars (and other bodies) carrying Raman, IR or LIBS spectrometers and give further clues about the potential habitability of Mars. We report, as an example, on the preservation potential of cyanobacterial photoprotective pigments (carotenoids) in the Antarctic cyanobacterium Nostoc cf. punctiforme strain CCCryo 231-06 after high doses of gamma irradiation and after space exposure [3]. [1] R. Moeller, M. Raguse, S. Leuko, T. Berger, C.E. Hellweg, A. Fujimori, R. Okayasu, and G. Horneck, Astrobiology, 17, 101–109 (2017). [2] J.-P. de Vera, M. Alawi, T. Backhaus, M. Baqué, D. Billi, U. Böttger, T. Berger, M. Bohmeier, C. Cockell, R. Demets, R. de la Torre Noetzel, H. Edwards, A. Elsaesser, C. Fagliarone, A. Fiedler, B. Foing, F. Foucher, J. Fritz, F. Hanke, et al., Astrobiology, 19, 145–157 (2019). [3] M. Baqué, F. Hanke, U. Böttger, T. Leya, R. Moeller, and J.-P. de Vera, Journal of Raman Spectroscopy, 49, 1617–1627 (2018).

The future search-for-life missions to Mars - ESA/Roscosmos’s ExoMars2020 and NASA’s Mars2020 rovers - will carry Raman spectrometers for in situ analysis of extraterrestrial material for the first time1,2. The question remains whether signs of extinct or extant life could be detected by this method. From our terrestrial examples, carotenoids (e.g. serving in cyanobacteria as accessory and photoprotective pigments) have been extensively used as biosignature models due to their stability and easy identification by Raman spectroscopy with a 532nm excitation wavelength3. Evaluating the detection limit of pigments under simulated extraterrestrial conditions is beneficial for the success of future life-detection missions. Ionizing radiation can be considered the most deleterious factor for the long term preservation of potential biomarkers on Mars4. Here, we report on the preservation potential of Raman signatures in the Antarctic cyanobacterium Nostoc sp. strain CCCryo 231–06 after high doses of gamma irradiation performed in the frame of the STARLIFE project5. The carotenoids' signals usually dominate the Raman spectra at 532nm excitation wavelength due to resonance effects. But comparing their distribution and quantifying their preservation is still problematic in natural samples. To standardize the analyses, we successfully applied Raman mapping and signal-to-noise ratios (SNR) masks to quantify the effects of irradiation. The typical in vivo Raman signatures of carotenoids could be detected even after exposure to up to 56 kGy with significant deterioration in terms of signal coverage and SNR. However, for colonies embedded in two different Martian mineral analogues (phyllosilicatic and sulfatic Mars regolith simulants), the carotenoids' signatures remained detectable even after the highest dose of γ-rays (117kGy) tested in this study, with no significant effect on signal coverage or SNRs. Carotenoids proved again their scientific value as model biosignatures for future life detection missions on Mars. Data gathered during these ground-based irradiation experiments contribute to interpret results from space experiments (such as BIOMEX6) and will guide our search for life on Mars and other bodies of interest.

Polygonally fractured ground is widespread at middle and high latitudes on Mars. The latitude-dependence and the morphologic similarity to terrestrial patterned ground in permafrost regions may indicate a formation as thermal contraction cracks, but the exact formation mechanisms are still unclear. In particular, it is debated whether freeze-thaw processes and liquid water are required to generate the observed features. This study quantitatively investigates polygonal networks in ice-free parts of continental Antarctica to help distinguishing between different hypotheses of their origin on Mars. The study site is located in the Helliwell Hills in Northern Victoria Land (�71.73�S/161.38�E) and was visited in the framework of the GANOVEX XI expedition during the austral summer of 2015/2016. The local bedrock consists mostly of sediments (sandstones) of the Beacon Supergroup and mafic igneous intrusions (Ferrar Dolerites). The surfaces are covered by glacial drift consisting of clasts with diverse lithologies. Thermal contraction cracks are ubiquitous.We mapped polygons in the northern part of Helliwell Hills in a GIS environment on the basis of high-resolution satellite images with a pixel size of �50 cm. The measured spatial parameters include polygon area, perimeter, length, width, circularity and aspect.We also analyzed the connectivity of enclosed polygons within a polygon network. The polygons do not display significant local relief, but overall the polygon centers are slightly higher than the bounding cracks (i.e. high-center polygons). Sizes of polygons can vary widely, dependent on the geographical location, between 10m2 and >900m2. In planar and level areas, thermal contraction cracks tend to be well connected as hexagonal or irregular polygonal networks without a preferred alignment. In contrast, polygonal networks on slopes form elongated, orthogonal primary cracks, which are either parallel or transverse to the steepest topographic gradient. During fieldwork, excavations were made in the center of polygons and across the bounding cracks. Typically, the uppermost �40 cm of regolith are dry and unconsolidated. Below that, there is commonly a sharp transition to ice-cemented material or very clear ice with no bubbles. Soil profiles were recorded, and sediment samples were taken and analyzed for their grain size composition with laser diffractometric measurement methods. External factors such as slope gradient and orientation, insolation and composition of surface and subsurface materials were included in the analysis.

Polygonal fractured ground is widespread at middle and high latitudes on Mars. The latitude-dependence and the morphologic similarity to terrestrial patterned ground in permafrost regions may indicate a formation as thermal contraction cracks, but the exact formation mechanisms are still unclear. This study quantitatively investigates polygonal networks in icefree parts of continental Antarctica to help distinguishing between different hypotheses of their origin on Mars.

Most studies using Antarctica as a Mars analogue have focused on the McMurdo Dry Valleys, which are among the coldest and driest places on Earth. However, other ice-free areas in continental Antarctica also display landforms that can inform the study of the possible geomorphic impact of water in a polar desert. Here we present a new analogue site in the interior of the Transantarctic Mountains in Northern Victoria Land. Gullies show unambiguous evidence for debris flows, and water tracks act as shallow subsurface pathways of water on top of the permafrost tale. Both processes are driven by meltwater from glacier ice and snow in an environment which never experiences rainfall and in which the air temperatures probably never exceed 0°C.

The challenge in astrobiology and planetary research in the near future is to realize space missions to study the habitability of Mars and the icy moons of the Jovian and Saturnian systems. Mars is an interesting object to search for habitable environments and for fossilized (and potentially present) life because of its past water driven wet history. On the other hand the Jovian moon Europa and the Saturnian moon Enceladus are promising candidates, where liquid water oceans beneath the surface are expected. These oceans can be habitable environments and the next challenge is to search there for present life. Some examples on potential biospheres and their biosignatures in Mars-like environments and in environmental conditions with reference to the icy moons will be given, which might exist in such kind of icy environments.

The main goal for astrobiologists is to find traces of present or past life in extraterrestrial environment or in meteorites. Biomolecules, such as lipids, pigments or polysaccharides, may be useful to establish the presence of extant or extinct life (Simoneit, B et al., 1998). BIOMEX (Biology and Mars Experiment) aims to measure to what extent biomolecules, such as pigments and cellular components, preserve their stability under space and Mars-like conditions. The experiment has just been launched in the space and will be exposed on EXPOSE-R payload to the outside of the International Space Station (ISS) for about 2 years. Among a number of extremophilic microorganisms tested, the Antarctic cryptoendolithic black fungus Cryomyces antarcticus CCFEE 515 was included in the experiment. The fungus, living in the airspaces of porous rocks, was already chosen in previous astrobiological investigation for studying the interplanetary transfer of life via meteorites. In that context, the fungus survived 18 months of exposure outside of the ISS (Onofri al., 2012); for all these reasons it is considered an optimal eukaryotic model for astrobiological exploration. Before launch dried samples were exposed, in ground based experiments, to extreme conditions, including vacuum, irradiation and temperature cycles.Upon sample re-hydration and survival analysis, including colony forming ability, Propidium MonoAzide (PMA) assay-coupled quantitative PCR (Mohapatra and La Duc, 2012) all the test systems survived, neither any DNA damage was detectable. Our analyses focused also on mineral-microorganisms interactions and stability/degradation of typical fungal macromolecules, in particular melanin, when exposed to space and simulated Martian conditions, contributing to the development of libraries of biosignatures in rocks, supporting future exploration missions.

One of the main challenges in astrobiology and planetary research in the near future is to realize space missions to study the habitability of Mars and the icy moons of the Jovian and Saturnian system. Mars is an interesting object to search for fossilized life because of its past water driven wet history. River beds, sedimentary deposits indicating the presence of lakes [1] as well as a supposed but highly debated presence of a former ocean on the north hemisphere [2] are clearly showing that the atmosphere must have been much denser and the conditions much more habitable than nowadays. Even today still water activity is present in specific niches on the surface of Mars [3]. This leads to the conclusion that the search for habitable environments on Mars and the presence of bio-traces of extinct or extant life is a reasonable enterprise to be conducted in the next space missions. Besides the planet Mars other planetary objects in our solar system are promising candidates to find life as there are the icy moons. The Jovian moon Europa is one promising candidate, where water driven resurfacing activity of its icy crust must regularly happen because of the low amount of impact craters on the surface as well as the clear observations of cryo-volcanos which can only be explained by the presence of a liquid water ocean beneath the surface. Fissures and cracks with colored salty deposits coming from the inner side of the supposed global ocean are also clearly showing that this ocean can be a habitable environment [4] and where it would be good to search for present life. The Saturnian moon Eneladus seems also to be a promising candidate to search for life. On this moon high water plumes come out of an ocean covered by its ice crust [5]. Some observations by the probe of Cassini also have shown, that besides the presence of water and salts a high number of simple and complex organics was observed within these plumes. Also for the Saturnian moon Titan an ocean is supposed beneath the icy crust and this moon has not to be neglected in future astrobiology-driven exploration missions. Because of these very important observations of the last decades international and interdisciplinary scientific teams are working on new types of space missions with the main task to search for life. To realize these space missions, the scientific teams are combining work performed in planetary analog field sites with work in the lab and analysis performed in planetary simulation facilities as well as combined with research done in space on specific exposure facilities as there are satellites and the International Space Station (ISS). The technology developments and scientific approaches gained by this specific combined work performed in very extreme habitats try to solve problems which might occur if we would like to detect life on the other planets and moons in our solar system. For that, technology is used and tested in planetary analog environments like in the deep sea as well as in dry and cold deserts and different life detectors are developed and used during these field campaigns before testing them in space and using further in the next space exploration missions to Mars and the icy moons. Taken into account the international planetary protection guidelines which clearly formulate to first prevent contamination of a planets and moons and their special regions which might be habitable before sending probes on the surface, important work for cleaning and sterilizing the complex technology is necessary and sometimes a big challenge for engineers to fulfill these guidelines.

One of the main challenges in astrobiology and planetary research in the near future is to realize space missions to study the habitability of Mars and the icy moons of the Jovian and Saturnian system. Mars is an interesting object to search for fossilized life because of its much more water driven wet history of its past. River beds, sedimentary deposits indicating the presence of lakes [1] as well as a sup-posed but highly debated presence of a former ocean on the north hemisphere [2] are clearly showing that the atmosphere must have been much denser and the conditions much more habitable than nowadays. Even today still water activity is present in specific niches on the surface of Mars [3]. This leads to the conclusion that the search for habitable environ-ments on Mars and the presence of bio-traces of extinct or extant life is a reasonable enterprise to be conducted in the next space missions. But Mars is not the only promising can-didate to find life in our solar system. The icy moons, like the Jovian moon Europa where water driven resurfacing activity must regularly happen because of the low amount of impact craters on the icy crusts as well as the clear observations of cryo-volcans and fissures and cracks with colored deposits coming from the inner side of a global ocean are clearly showing, that the ocean can be a habitable environment [4]. The Saturnian moon Eneladus seems also be a promising candidate to search for life. On this moon high water plumes come out of an ocean covered by its ice crust [5]. Some observations by the probe of Cassini also have shown, that besides the presence of water and salts a high number of simple and complex organics was observed within these plumes. Also for the Saturnian moon Titan an ocean is supposed beneth the icy crust and this moon has not to be neglected in future astrobiology-driven exploration missions. Because of these very important observations of the last decades international and interdisciplinary scientific teams are working on new types of space missions with the main task to search for life including work performed in planetary analog field sites, work in the lab and analysis performed in planetary simulation facilities combined with research done in space on specific exposure facilities as there are satellites and the International Space Station (ISS). The technology developments and scientific approaches try to solve problems which might occur if we would like to detect life. For that technology is used and tested in planetary analog environ-ments like in the deep sea as well as in dry and cold deserts and different life detectors are developed and used during these field campaigns before testing them in space and using further in the next space exploration missions to Mars and the icy moons. Taken into account the international plan-etary protection guidelines which clearly formulate to first prevent contamination of a planets and moons and their spe-cial regions which might be habitable before sending probes on the surface, important work for cleaning and sterilizing the complex technology is necessary and sometimes a big chal-lenge for engineers to fulfill these guidelines.

New results on extremophiles and observations of Mars missions regarding the detailed mineralogy, the occurrence of water in the equatorial region of Mars [1-3], new announcements of MSL findings and their implications for the surface condi-tions at Gale crater [4, 5] as well as measurements of the Mars surface radiation environment [6] fuel the debate about possible developments of life on Mars. Based on previous studies [7-8] we examined water vapor interaction and water-bearing properties of B. frigida before and after UVC irradiation. The meas-urements have been partially conducted after simula-tion of environmental conditions which are supposed to be Mars-like. Lichens are symbiotic organisms that are able to colonize a broad range of extreme habitats and, therefore, represent useful model systems in as-trobiological research. Our aim is to contribute to an improved under-standing of extremophiles under exobiological aspects within the frame of BIOMEX (Biology and Mars Ex-periment) at the ISS, in respect to irradiation effects on water retention properties. The results may also sup-port data evaluation of in-situ missions such as MSL and ExoMars. References: [1] Feldmann W.C. et al. (2004) JGR 109 E 09006. [2] Bibring, J.-P. et al. Science 307, 1576-1581. [3] Poulet F. et al. (2005) Nature 438, 623- 627. [4] Vaniman D.T. et al. (2013) Science DOI: 10.1126/science.1243480. [5] Ming D.W. et al. (2013) Science DOI: 10.1126/science.1245267 [6] Hassler D.M. et al. (2013) Science DOI: 10.1126/science. 1244797.[7] Jänchen J. et al. (2006) Icarus, 180, 353- 358. [8] Jänchen J. et al. (2013) 44th LPSC Abstract No. 1504.

Mars is a frozen desert planet. Considerable intense UV radiation fluxes reach its surface and with its thin and 95 % CO2 rich atmosphere and an atmospheric pressure of approximately 6 mbar this planet is not supposed to be habitable. But according to a variety of different experiments during the last decade where microorganisms were investigated under Mars-like environmental conditions there is evidence that even recent Mars appears to be a habitable planet. The habitability of the surface and upper subsurface of Mars depends on one hand on the viability and adaptation capacity of microorganisms under Mars-like environments and on the other hand on the planet's energy resources and liquid water availability. Besides chemical, inorganic energy sources in the soil intense solar radiation is available as additional energy source on the surface of Mars but might be harmful for most of known terrestrial life forms. However, previous studies on extremophilic microorganisms which were performed on space exposure platforms (e.g. BIOPAN on the satellite FOTON and EXPOSE on ISS) show the high resistance of tested bacteria, archaea and lichens to space radiation and desiccation caused by vacuum. During Mars simulation experiments photosynthesizing microorganisms are even able to do photosynthesis periodically. The periodicity of the photosynthetic activity depends on the diurnal cycle with its varying temperatures and relative humidity. It is important to emphasize that the aforementioned space resistant microorganisms are mainly collected in polar and alpine habitats. They are living in permafrost regions with high UV radiation income and extreme dryness provoking high adaptation strategies. Because of these environmental parameters the alpine, desert and polar habitats were characterized as Mars analogue. The Mars analogy of these regions can also be justified by comparing the colonized alpine and polar field profiles with surface structures on Mars. Numerous investigations were done during field campaigns in the Alps, the Arctic (Svalbard) and in Antarctica. Based on these field investigations it becomes obvious that gullies, polygon rich regions and micro caves, fissures and cracks in rocks can be seen as suitable candidates for habitable areas on the surface of Mars in addition to the supposed ice rich environment in the subsurface. As mentioned above, the habitability of Mars depends also on the availability of liquid water. Due to the presence of salts and perchlorate rich soils on Mars water can for sufficient relative humidity remain in a liquid phase, forming at least temporary liquid cryobrines far below the freezing point, which e.g. might be useful for some halophilic microorganisms. This may be in favour of the habitability of the Martian surface. In addition the habitability can also be influenced by the sorption and desorption capacity of other soil particles. These particles and salty solutions could avoid or enhance the liquid phase of water. Processes enhancing the liquefaction of water might explain the recently observed rheological events provoking e.g. the formation of gullies on the surface of Mars which are known as real habitats for a diversity of microorganisms on terrestrial martian analogue environments mostly present in the polar regions. All presently enumerated factors are positively emphasizing that habitability of recent Mars is particularly probable for some of terrestrial life forms.

The GANOVEX X expedition (German Antarcic North Victoria Land Expedition) in the Antarctic summer season 2009/2010 took place on the Antarctic continent. Besides analysis on the geological formations, the distribution of microorganisms as lichens, fungi, green alga and cyanobacteria has been studied along a longitudinal and altitude transect. A diversity of micro-niches has been discovered. Cosmopolites and endemic microorganisms developed adaptation strategies to colonize retreat areas of eroded surfaces, fissures and cracks of granite, volcanic and metamorphic rocks in permafrost regions. These specific habitats were additionally characterized by measurements of the macro- and microclimate (UV-, IR-, VIS-/PAR- radiation, humidity, temperature, atmospheric ozone, water and aerosol content). Based on the discoveries in the mentioned area of the Transantarctic Mountains and due to comparisons to previous results obtained from some of the space-exposed cosmopolites in the space experiments “Lithopanspermia” on BIOPAN 6 / FOTON M3 satellite and “LIFE” on EXPOSE on the International Space Station (ISS) as well as from Mars simulations at the HUMILAB (DLR Berlin), we conclude, that these investigated microorganisms from the Antarctic transect as well as from Spitsbergen and from alpine regions can be characterized as resistant to Mars conditions and that the recent Mars is probably still a habitable planet for Arctic, Antarctic and alpine microorganisms.

Recent Mars observations and experimental investigations indicate that water could be a key factor of current physical and chemical processes on the martian surface, e.g. rheological phenomena. Therefore it is of particular interest to get information about the liquid like state of water on martian analog soils in the temperature range below 0 ◦C. In this context, a plate capacitor has been developed to obtain isothermal dielectric spectra of fine grained soils in the frequency range from 10 Hz to 1.1 MHz at martian like temperatures down to -70 °C. Two martian analogue soils have been investigated: a Ca-Bentonit (specific surface of 215 m2/g, up to 9.4 %w/w gravimetric water content) and JSC Mars 1, a volcanic ash (specific surface of 146 m2/g, up to 7.4 %w/w). Three soil-specific relaxation processes are observed in the investigated frequency-temperature range: two weak high frequency processes (bound or confined water as well as ice) and a strong low frequency process due to counter ion relaxation and the Maxwell-Wagner effect. The real part of effective complex soil permittivity at 350 kHz was used to determine ice and liquid like water content by means of the Birchak or CRIM equation. There are evidence that bentonite down to -70 °C has a liquid like water content of 1.3 mono layers and JSC Mars 1 a liquid like water content of 2.3 mono layers.