Results on the survival of cryptobiotic cyanobacteria samples after exposure to Mars-like environmental conditions J. -P. de Vera 1 , S. Dulai 2 , A. Kereszturi 3,4 , L. Koncz 1 , A. Lorek 1 , D. Mohlmann 1 , M. Marschall 1,2 and T. Pocs 2 1 German Aerospace Center (DLR), Institute of Planetary Research, Berlin, Germany 2 Departments of Plant Physiology and Botany, Eszterhazy Karoly College, Eger, Hungary 3 New Europe School for Theoretical Biology and Ecology, Hungary 4 Konkoly Thege Miklos Astronomical Institute, Research Centre for Astronomy and Earth Sciences, Hungary e-mail: kereszturi.akos@csfk.mta.hu Abstract: Tests on cyanobacteria communities embedded in cryptobiotic crusts collected in hot and cold deserts on Earth were performed under Mars-like conditions. The simulations were realized as a survey, to find the best samples for future research. During the tests organisms have to resist Mars-like conditions such as atmospheric composition, pressure, variable humidity (saturated and dry conditions) and partly strong UV irradiation. Organisms were tested within their original habitat inside the crust. Nearly half of the cryptobiotic samples from various sites showed survival of a substantial part of their coexisting organisms. The survival in general depended more on the nature of the original habitat and type of the sample than on the different conditions they were exposed to. The best survival was observed in samples from United Arab Emirates (Jebel Ali, 25 km SW of Dubai town) and from Western Australia (near the South edge of Lake Barley), by taxa: Tolypothrix byssoidea, Gloeocapsopsis pleurocapsoides, Nostoc microscopicum, Leptolyngbya or Symploca sp. At both places in salty desert areas members of the Chenopodiaceae family dominated among the higher plants and in the cryptobiotic crust cyanobacterial taxa Tolypothrix was dominant. These organisms were all living in salty locations with dry conditions most of the year. Among them Tolypothrix, Gloeocapsopsis and Symploca sp. were tested in Mars simulation chambers for the first time. The results suggest that extremophiles should be tested with taken into account the context of their original microenvironment, and also the importance to analyse communities of microbes beside single organisms. Received 12 July 2013, accepted 11 August 2013, first published online 17 October 2013 Key words: extremophiles, cyanobacteria, cryptobiotic crust, Mars, simulation. Introduction An important step towards the understanding if Earth-like life is able to survive on Mars and what kind of steps should be taken to realize planetary protection is the realization of analysis on the survival of microbes under Mars-like conditions. In this work, we present the results of our Mars simulation tests performed in the DLR Mars Simulation Facility (DLR-MSF), Berlin. The aim of this study is to analyse the survival after being exposed to different conditions we might encounter on Mars, as there are various parameters such as very low temperatures, gas composition, low gas pressure, low amounts of relative humidity and exposure to UV irradiation that might have important effects on many organisms. The parameters were adjusted artificially and were computer controlled and monitored by the use of a set of sensors inside the simulation chamber. We realized survey-like analysis on the survival of different cyanobacteria. We are interested in the analysis of microbes inside cryptobiotic crusts, where several taxa of cyanobacteria are present in between mineral grains and weathering products, providing a small but complex ideal environment for survival in extreme conditions. Besides the simulation results, we also put emphasis on the possible benefits of realizing Mars-like simulation chamber tests with microbes embedded in their natural microenvironment (cryptobiotic crust) and to highlight the Mars relevant issues of these crusts. Using the experiences an outlook on an optimized realization of future chamber tests will be given. Cryptobiotic crusts as microhabitats The survival of cyanobacteria inside cryptobiotic crust samples was analysed. A cryptobiotic crust is often also called as microbiotic soil crust (Eldridge & Greene 1994), ‘biological soil crust’ (Belnap et al. 2001) or ‘cryptogamic crust’ (Strandling et al. 2002). We use the term of ‘cryptobiotic crust’ for the 0.05–5 mm thin layer on isolated or somewhere in shadowed rock surfaces on Earth, composed of weathered minerals and cryptogamic organisms (bacteria, algae, small sized fungi, lichens and small-sized bryophytes) embedded in a mucilagineous sheath (envelope) of cyanobacteria, algae and International Journal of Astrobiology 13 (1): 35–44 (2014) doi:10.1017/S1473550413000323 © Cambridge University Press 2013