Astrobiology and Habitability Studies in Preparation for Future Mars Missions: Trends from Investigating Minerals, Organics and Biota
Total Page：16
File Type：pdf, Size：1020Kb
International Journal of Astrobiology 10 (3): 239–253 (2011) 239 doi:10.1017/S1473550411000140 © Cambridge University Press 2011 Astrobiology and habitability studies in preparation for future Mars missions: trends from investigating minerals, organics and biota P. Ehrenfreund1,2, W.F.M. Röling3, C.S. Thiel4, R. Quinn5, M.A. Sephton6, C. Stoker5, J.M. Kotler1, S.O.L. Direito3, Z. Martins6, G.E. Orzechowska7, R.D. Kidd7, C.A van Sluis8 and B.H. Foing9 1Leiden Institute of Chemistry, PO Box 9502, 2300 Leiden, The Netherlands e-mail: [email protected] 2Space Policy Institute, Elliott School of International Affairs, Washington, DC, USA 3Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam, The Netherlands 4Institute of Medical Physics and Biophysics, CeNTech, University of Münster, 48149, Münster, Germany 5NASA Ames Research Center, Moffett Field, CA 94035, USA 6Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK 7Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA 8Department of Biotechnology, Delft University of Technology, 2628 BC Delft, The Netherlands 9ESA ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands Abstract: Several robotic exploration missions will travel to Mars during this decade to investigate habitability and the possible presence of life. Field research at Mars analogue sites such as desert environments can provide important constraints for instrument calibration, landing site strategies and expected life detection targets. We have characterized the mineralogy, organic chemistry and microbiology of ten selected sample sites from the Utah desert in close vicinity to the Mars Desert Research Station (MDRS) during the EuroGeoMars 2009 campaign (organized by International Lunar Exploration Working Group (ILEWG), NASA Ames and ESA ESTEC). Compared with extremely arid deserts (such as the Atacama), organic and biological materials can be identified in a larger number of samples and subsequently be used to perform correlation studies. Among the important findings of this field research campaign are the diversity in the mineralogical composition of soil samples even when collected in close proximity, the low abundances of detectable polycyclic aromatic hydrocarbons (PAHs) and amino acids and the presence of biota of all three domains of life with significant heterogeneity. An extraordinary variety of putative extremophiles, mainly Bacteria and also Archaea and Eukarya was observed. The dominant factor in measurable bacterial abundance seems to be soil porosity and lower small (clay-sized) particle content. However, correlations between many measured parameters are difficult to establish. Field research conducted during the EuroGeoMars 2009 campaign shows that the geological history and depositional environment of the region, as well as the mineralogy influence the ability to detect compounds such as amino acids and DNA. Clays are known to strongly absorb and bind organic molecules often preventing extraction by even sophisticated laboratory methods. Our results indicate the need for further development and optimization of extraction procedures that release biological compounds from host matrices to enable the effective detection of biomarkers during future sampling campaigns on Earth and Mars. Received 25 January 2011, accepted 1 April 2011, first published online 12 May 2011 Key words: astrobiology, habitability, life detection, field analogue research, Mars, organics, clays, landing site criteria. Introduction 2011 will explore the Martian surface, followed by the Mars Atmosphere and Volatile EvolutioN (MAVEN) space- The objective of future international planetary exploration craft, scheduled for launch in late 2013. A long-term ESA– programmes is to implement a long-term plan for the robotic NASA cooperation plan for the exploration of Mars with and later human exploration of the Moon, Mars and Near- missions in 2016 and 2018 has been recently developed that Earth Asteroids (NEOs). Mars is the central object of interest will investigate the atmosphere and the surface of Mars for for habitability studies and life detection beyond the Earth and signs of habitability and life and prepare for the Mars Sample can be visited frequently by robotic spacecrafts, paving the Return (MSR) mission (Grant et al. 2010). China will way for returned samples and human exploration. NASA’s contribute the Yinghou-1 (YH-1) orbiter to the Russian Mars Science Laboratory (MSL) to be launched in November Phobos-Grunt sample return mission in 2011 and conduct 240 P. Ehrenfreund et al. space-environment, atmospheric, gravity and surface-imaging of culturable biomass in Yungay soils. The total organic con- studies of Mars. tent (TOC) was estimated between 560 and 765 ppm. Connon Our knowledge about planet Mars has benefited over the last et al. (2007) studied the bacterial diversity in the Atacama few decades from a fleet of orbital and landed spacecraft such Desert and detected Actinobacteria, Protobacteria, Firmicutes as Mars Global Surveyor, Mars Odyssey, the Mars Explo- and TM7. ration Rovers, Mars Express and the Mars Reconnaissance In this paper, we report on astrobiology field research from Orbiter. Results from these missions indicate that Mars had a the Mars Desert Research Station (MDRS) in Hanksville, different climate in the past. On ancient Mars water was Utah conducted during the EuroGeoMars 2009 campaign persistent in shallow surface bodies, lakes, connected networks (Foing et al. 2011). MDRS is located in a geological formation and as groundwater near the surface (Malin et al. 2003; Knoll that was formed 150 million years ago (Hintze & Kowallis & Grotzinger 2006; Murchie et al. 2009; Squyres et al. 2009). 2009; Clarke & Stoker 2011). Geology close to the habitat A diverse suite of minerals, including hydrated sulphates, includes the Middle Jurassic Summerville Formation, the phyllosilicates and silica, produced during aqueous alteration Late Jurassic Morrison Formation, the Early Cretaceous of Martian crustal rocks has been identified both from orbit Dakota Sandstone and the middle Cretaceous Mancos Shale and from the Martian surface (e.g. Chevrier & Mathé 2007; Formations (Clarke & Stoker 2011; Stoker et al. 2011). Sedi- Arvidson et al. 2008; Hecht et al. 2009; Poulet et al. 2009). mentary deposits of sands, evaporites and clays are found; Recent observations with instruments onboard Mars Express gypsum and a variety of clay minerals have been detected and the Mars Reconnaissance orbiters identified more (Borst et al. 2010). In addition, MDRS is located in an area than 990 hydrated mineral exposures on Mars (Carter et al. characterized by red-coloured hills, soils and sandstones due to 2011). At the Mawrth Vallis region, phyllosilicate units are the presence of iron oxides (e.g. haematite) (Chan et al. 2004; observed that resemble terrestrial sedimentary deposits Ormö et al. 2004). We have investigated ten selected samples (Bishop et al. 2011). Recent Earth-based observations have from different geological formations (Mancos Shale, Morrison detected methane in the atmosphere of Mars (e.g. Formisano and Dakota) and also chose a variety of locations (surface, et al. 2004; Mumma et al. 2009). Zahnle et al. (2011) critically subsurface and cliffs) for mineralogy, organic content and review these results and argue that variable methane on Mars biota (Direito et al. 2011; Kotler et al. 2011; Martins et al. is physically and chemically implausible. Results from the 2011; Orzechowska et al. 2011; Thiel et al. 2011a). In this Phoenix mission have yielded new insights into the compo- paper, we analyse the individual studies in an attempt to sition of the Martian soil. A slightly alkaline soil pH and establish correlations among environmental parameters and perchlorate as dominant soluble anion were determined by the biota. The results are interpreted in the context of future Phoenix Wet Chemical Laboratory (Hecht et al. 2009). CO2 missions that target the identification of organic molecules and release measured in the Thermal Evolved Gas Analyzer indi- biomarkers on Mars. cates the presence of calcium carbonate (Boynton et al. 2009). Robotic and human operations in space can be effectively Sample analysis prepared on Earth, as terrestrial extreme environments often provide analogues to landing and operation sites on the Moon Data from several studies on ten selected samples are compiled and Mars. Existing Earth-based field research programmes and compared in this paper, see Fig. 1. Soil samples were preparing for planetary exploration are diverse (Ansdell et al. collected under sterile conditions at desert areas of Utah in the 2011). Many space instruments augment their flight readiness vicinity of MDRS. The samples were partly analysed in situ level through tests in planetary analogue regions on Earth. and later distributed to the various laboratories for subsequent Lessons learned from sample collection, handling and in-situ analysis of mineralogy, organic content and microbiology. analysis at these sites help to overcome contamination issues as Soil sample properties that were measured in the MDRS well as improve instrument performance. Using Mars regolith habitat laboratory included pH and elemental composition of analogues to test physical and chemical properties such as pH, nitrate, potassium (K), phosphorous (P) and magnesium (Mg) redox potential, elemental composition, conductivity and (Table 1). For the pH measurements, the soil