The resistance of the lichen Circinaria gyrosa (nom. provis.) towards simulated Mars conditions—a model test for the survival capacity of an eukaryotic extremophile F.J. Sa´ nchez a,n , E. Mateo-Martı´ b , J. Raggio c , J. Meeßen d , J. Martı´nez-Frı´as b , L.G a . Sancho c , S. Ott d , R. de la Torre a a Instituto Nacional de Te´cnica Aeroespacial (INTA), Ctra. de Ajalvir km. 4, 28850-Torrejo´n de Ardoz, Madrid, Spain b Centro de Astrobiologı ´a (CAB) (INTA-CSIC), Ctra. de Ajalvir km. 4, 28850-Torrejo´n de Ardoz, Madrid, Spain c Departamento de Biologı ´a Vegetal II, Facultad de Farmacia, Universidad Complutense de Madrid (UCM), 28040-Madrid, Spain d Institute of Botany, Heinrich-Heine University, Universit¨ atsstr.1, 40225-D¨ usseldorf, Germany article info Article history: Received 23 December 2011 Received in revised form 30 July 2012 Accepted 3 August 2012 Available online 21 August 2012 Keywords: Planetary Atmospheres and Surfaces Chamber (PASC) Mars Lichens Symbiosis Survival Resistance potential abstract The ‘‘Planetary Atmospheres and Surfaces Chamber’’ (PASC, at Centro de Astrobiologı´a, INTA, Madrid) is able to simulate the atmosphere and surface temperature of most of the solar system planets. PASC is especially appropriate to study irradiation induced changes of geological, chemical, and biological samples under a wide range of controlled atmospheric and temperature conditions. Therefore, PASC is a valid method to test the resistance potential of extremophile organisms under diverse harsh conditions and thus assess the habitability of extraterrestrial environments. In the present study, we have investigated the resistance of a symbiotic organism under simulated Mars conditions, exemplified with the lichen Circinaria gyrosa—an extremophilic eukaryote. After 120 hours of exposure to simulated but representative Mars atmosphere, temperature, pressure and UV conditions; an unaltered photosynthetic performance demonstrated high resistance of the lichen photobiont. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Nowadays, the study of planetary environments has become a major scientific interest, especially with respect to the possibility of extinct or extant life (Davila et al., 2010). Planetary objects, like Mars, are priority targets for searching bio-signatures in our solar system. This is mainly due to the recently demonstrated presence of water in any of their past or present geological periods (Horneck, 2000; McKay, 1997; Mehta et al., 2011; Nelli et al., 2010). However, the effect at the planetary surfaces of environ- mental parameters such as radiation, gas composition, pressure, and temperature is critical either for survival of microorganisms or for the likelihood of preserving bio-signatures (Nelli et al., 2010; Patel et al., 2004). The modest knowledge that we have about planetary environ- ments comes mainly from space missions, which are highly con- suming both, time and cost. Due to the obvious technical and economical limitations of in-situ planetary exploration, laboratory simulations are the most feasible options to make advances, both in planetary science and astrobiological approaches. These facilities evolved rapidly and now are able to mimic the conditions found in the atmospheres and on the surfaces of planetary objects as Mars, Titan, and Europa (Galletta et al., 2006; Jensen et al., 2008; Mateo- Martı´ et al., 2006; Zhukova et al., 1965; Zill et al., 1979), especially by providing controlled conditions, analytical protocols, as well as sensors (Garry et al., 2006; Nicholson and Schuerger, 2005; Sears et al., 2002; Smith et al., 2009). Additionally, state-of-the-art facil- ities as PASC, allow to discriminate between the effects of individual physical parameters and selected combinations, and are precious for mission preparation and ground reference tests. PASC has provided valuable scientific outcome related to astrobiology and habitability research: In previous studies, the UV-absorbing properties of Martian analog basaltic dust as a function of its mass and thickness (Mun˜oz-Caro et al., 2006) have been determined. Studies on the stability of saline water under present-day Mars conditions indicate that salty environments might allow water to be locally and sporadically liquid on Mars (Zorzano et al., 2009). Additionally, the survival of chemolithoau- totrophic bacteria exposed to simulated Mars environmental conditions was recently demonstrated (Go´ mez et al., 2010). Life Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/pss Planetary and Space Science 0032-0633/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.pss.2012.08.005 n Corresponding author. Tel.: þ34 91 52 01656. E-mail address: sanchezifj@inta.es (F.J. Sa´ nchez). Planetary and Space Science 72 (2012) 102–110