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On November 5–8, 2019, the “Mars Extant Life: What's Next?” conference was convened in Carlsbad, New Mexico. The conference gathered a community of actively publishing experts in disciplines related to habitability and astrobiology. Primary conclusions are as follows: A significant subset of conference attendees concluded that there is a realistic possibility that Mars hosts indigenous microbial life. A powerful theme that permeated the conference is that the key to the search for martian extant life lies in identifying and exploring refugia (“oases”), where conditions are either permanently or episodically significantly more hospitable than average. Based on our existing knowledge of Mars, conference participants highlighted four potential martian refugium (not listed in priority order): Caves, Deep Subsurface, Ices, and Salts. The conference group did not attempt to reach a consensus prioritization of these candidate environments, but instead felt that a defensible prioritization would require a future competitive process. Within the context of these candidate environments, we identified a variety of geological search strategies that could narrow the search space. Additionally, we summarized a number of measurement techniques that could be used to detect evidence of extant life (if present). Again, it was not within the scope of the conference to prioritize these measurement techniques—that is best left for the competitive process. We specifically note that the number and sensitivity of detection methods that could be implemented if samples were returned to Earth greatly exceed the methodologies that could be used at Mars. Finally, important lessons to guide extant life search processes can be derived both from experiments carried out in terrestrial laboratories and analog field sites and from theoretical modeling.

The Joint Workshop on Induced Special Regions convened scientists and planetary protection experts to assess the potential of inducing special regions through lander or rover activity. An Induced Special Region is defined as a place where the presence of the spacecraft could induce water activity and temperature to be sufficiently high and persist for long enough to plausibly harbor life. The questions the workshop participants addressed were: (1) What is a safe stand-off distance, or formula to derive a safe distance, to a purported special region? (2) Questions about RTGs (Radioisotope Thermoelectric Generator), other heat sources, and their ability to induce special regions. (3) Is it possible to have an infected area on Mars that does not contaminate the rest of Mars? The workshop participants reached a general consensus addressing the posed questions, in summary: (1) While a spacecraft on the surface of Mars may not be able to explore a special region during the prime mission, the safe stand-off distance would decrease with time because the sterilizing environment, that is the martian surface would progressively clean the exposed surfaces. However, the analysis supporting such an exploration should ensure that the risk to exposing interior portions of the spacecraft (i.e., essentially unsterilized) to the martian surface is minimized. (2) An RTG at the surface of Mars would not create a Special Region but the short-term result depends on kinetics of melting, freezing, deliquescence, and desiccation. While a buried RTG could induce a Special Region, it would not pose a long-term contamination threat to Mars, with the possible exception of a migrating RTG in an icy deposit. (3) Induced Special Regions can allow microbial replication to occur (by definition), but such replication at the surface is unlikely to globally contaminate Mars. An induced subsurface Special Region would be isolated and microbial transport away from subsurface site is highly improbable.

K(+), Na(+), Ca(2+), Mg(2+), Fe(2+), Fe(3+), and Al(3+) perchlorate salts were studied to provide spectral and thermal data for detecting and characterizing their possible presence on Mars. Spectral and thermal analyses are coordinated with structural analyses to understand how different cations and different hydration levels affect the mineral system. Near-infrared (NIR) spectral features for perchlorates are dominated by H(2)O bands that occur at 0.978–1.01, 1.17–1.19, 1.42–1.48, 1.93–1.99, and 2.40–2.45 μm. Mid-IR spectral features are observed for vibrations of the tetrahedral [Formula: see text] ion and occur as reflectance peaks at 1105–1130 cm(−1) (~8.6–9 μm), 760–825 cm(−1) (~12–13 μm), 630 cm(−1) (~15.9 μm), 460–495 (~20–22 μm), and 130–215 (~50–75 μm). The spectral bands in both regions are sensitive to the type of cation present because the polarizing power is related to the band center for many of the spectral features. Band assignments were confirmed for many of the spectral features due to opposing trends in vibrational energies for the [Formula: see text] and H(2)O groups connected to different octahedral cations. Differential scanning calorimetry (DSC) data show variable patterns of water loss and thermal decomposition temperatures for perchlorates with different cations, consistent with changes in spectral features measured under varying hydration conditions. Results of the DSC analyses indicate that the bond energies of H(2)O in perchlorates are different for each cation and hydration state. Structural parameters are available for Mg perchlorates (Robertson and Bish 2010) and the changes in structure due to hydration state are consistent with DSC parameters and spectral features. Analyses of changes in the Mg perchlorate structures with H(2)O content inform our understanding of the effects of hydration on other perchlorates, for which the specific structures are less well defined. Spectra of the hydrated Fe(2+) and Fe(3+) perchlorates changed significantly upon heating to 100 °C or measurement under low-moisture conditions indicating that they are less stable than other perchlorates under dehydrated conditions. The perchlorate abundances observed by Phoenix and MSL are likely too low to be identified from orbit by CRISM, but may be sufficient to be identifiable by a VNIR imager on a future rover.

The present study demonstrates that γ-radiolyzed perchlorate-containing Mars soil salt analogues (in a CO2 atmosphere) generate upon H2O wetting the reactive oxygen species (ROS) superoxide radical (O2•-), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH). This study also validates that analogue radiolysis forms oxychlorine species that, in turn, can UV-photolyze to •OH upon UV photolysis. This investigation was made possible by the development of a new assay for inorganic-origin O2•- and H2O2 determination and by the modification of a previous assay for soil •OH. Results show that radiolyzed Mg(ClO4)2 generates H2O2 and •OH; and when included as part of a mixture analogous to the salt composition of samples analyzed at the Mars Phoenix site, the analogue generated O2•-, H2O2, and •OH, with •OH levels 150-fold higher than in the radiolyzed Mg(ClO4)2 samples. Radiolyzed Mars Phoenix site salt analogue that did not contain Mg(ClO4)2 generated only •OH also at 150-fold higher concentration than Mg(ClO4)2 alone. Additionally, UV photolysis of the perchlorate γ radiolysis product chlorite (ClO2-) generated the oxychlorine products trihalide (Cl3-), chlorine dioxide (ClO2•), and hypochlorite (ClO-), with the formation of •OH by UV photolysis of ClO-. While the generation of ROS may have contributed in part to 14CO2 production in the Viking Labeled Release (LR) experiment and O2 (g) release in the Viking Gas Exchange (GEx) experiment, our results indicate that they are not likely to be the major contributor to the LR and GEx results. However, due to their highly reactive nature, they are expected to play a significant role in the alteration of organics on Mars. Additionally, experiments with hypochlorite show that the thermal stability of NaClO is in the range of the thermal stability observed for thermally liable oxidant responsible for the Viking LR results. Key Words: Mars-Oxygen-Salts-Radiation-Habitability. Astrobiology 17, 319-336.

We describe the design of an instrument, the OxR (for Oxygen Release), for the enzymatically specific and non-enzymatic detection and quantification of the reactive oxidant species (ROS), superoxide radicals (O2&bull, &minus, ), and peroxides (O22&minus, e.g., H2O2) on the surface of Mars and Moon. The OxR instrument is designed to characterize planetary habitability, evaluate human health hazards, and identify sites with high biosignature preservation potential. The instrument can also be used for missions to the icy satellites of Saturn&rsquo, s Titan and Enceladus, and Jupiter&rsquo, s Europa. The principle of the OxR instrument is based on the conversion of (i) O2&bull, to O2 via its enzymatic dismutation (which also releases H2O2), and of (ii) H2O2 (free or released by the hydrolysis of peroxides and by the dismutation of O2&bull, ) to O2 via enzymatic decomposition. At stages i and ii, released O2 is quantitatively detected by an O2 sensor and stoichiometrically converted to moles of O2&bull, and H2O2. A non-enzymatic alternative approach is also designed. These methods serve as the design basis for the construction of a new small-footprint instrument for specific oxidant detection. The minimum detection limit of the OxR instrument for O2&bull, and O22&minus, in Mars, Lunar, and Titan regolith, and in Europa and Enceladus ice is projected to be 10 ppb. The methodology of the OxR instrument can be rapidly advanced to flight readiness by leveraging the Phoenix Wet Chemical Laboratory, or microfluidic sample processing technologies.

Mars landed and orbiter missions have instrumentation capable of detecting oxychlorine phases (e.g. perchlorate, chlorate) on the surface. Perchlorate (~0.6 wt%) was first detected by the Wet Chemistry Laboratory in the surface material at the Phoenix Mars Landing site. Subsequent analyses by the Thermal Evolved Gas Analyser aboard the same lander detected an oxygen release (~465°C) consistent with the thermal decomposition of perchlorate. Recent thermal analysis by the Mars Science Laboratory's Sample Analysis at Mars instrument has also indicated the presence of oxychlorine phases (up to 1.2 wt%) in Gale Crater materials. Despite being at detectable concentrations, the Chemistry and Mineralogy (CheMin) X-ray diffractometer has not detected oxychlorine phases. This suggests that Gale Crater oxychlorine may exist as poorly crystalline phases or that perchlorate/chlorate mixtures exist, so that individual oxychlorine concentrations are below CheMin detection limits (~1 wt%). Although not initially designed to detect oxychlorine phases, reinterpretation of Viking Gas Chromatography/Mass Spectrometer data also suggest that oxychlorine phases are present in the Viking surface materials. Remote near-infrared spectral analyses by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument indicate that at least some martian recurring slope lineae (RSL) have spectral signatures consistent with the presence of hydrated perchlorates or chlorates during the seasons when RSL are most extensive. Despite the thermal emission spectrometer, Thermal Emission Imaging System, Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité and CRISM detection of hundreds of anhydrous chloride (~10–25 vol%) deposits, expected associated oxychlorine phases (>5–10 vol%) have not been detected. Total Cl and oxychlorine data sets from the Phoenix Lander and the Mars Science Laboratory missions could be used to develop oxychlorine versus total Cl correlations, which may constrain oxychlorine concentrations at other locations on Mars by using total Cl determined by other missions (e.g. Viking, Pathfinder, MER and Odyssey). Development of microfluidic or ‘lab-on-a-chip’ instrumentation has the potential to be the next generation analytical capability used to identify and quantify individual oxychlorine species on future landed robotic missions to Mars.

This study presents an assay for the detection and quantification of soil metal superoxides and peroxides in regolith and soil. The O2 release (OR) assay is based on the enzymatic conversion of the hydrolysis products of metal oxides to O2, and their quantification by an O2 electrode based on the stoichiometry of the involved reactions: The intermediate product O2 from the hydrolysis of metal superoxides is converted by cytochrome c to O2, and also by superoxide dismutase (SOD) to 1/2 mol O2 and 1/2 mol H2O2, which is then converted by catalase (CAT) to 1/2 mol O2. The product H2O2 from the hydrolysis of metal peroxides and hydroperoxides is converted to 1/2 mol O2 by CAT. The assay-method was validated in a sealed sample chamber using a liquid-phase Clark-type O2 electrode with known concentrations of O2 and H2O2, and with commercial metal superoxide and peroxide mixed with Mars analogue Mojave and Atacama Desert soils. Carbonates and perchlorates, both present on Mars, do not interfere with the assay. The assay lower limit of detection, using luminescence quenching/optical sensing O2-electrodes, is 1 nmol O2 cm(exp. -3) or better. The activity of the assay enzymes SOD and cytochrome c was unaffected up to 6 Gy exposure by gamma-radiation, while CAT retained 100% and 40% of its activity at 3 and 6 Gy, respectively, demonstrating the suitability of these enzymes for planetary missions, e.g., in Mars or Europa.

A 3D-printed microfluidic device coupled with a fluidic processing system was developed to enable autonomous end-to-end sample handling and electrochemical characterization of an ocean world analogue solution – synthetic seawater (SW). This dual-channel microfluidic cell was populated with 14 electrodes and performed electrochemical measurements similar to those used in the MECA Wet Chemistry Laboratory on board NASA’s Phoenix Lander that landed on Mars in 2008. Biological and metallic redox events were evaluated using cyclic voltammetry with Au, Pt, and glassy carbon electrodes, with the latter displaying superior sensitivity and selectivity. Conductivity and pH were measured using Pt and iridium oxide electrodes respectively, and SW anions such as chloride were quantified using chronopotentiometry with a Ag electrode. The fluidic handling system demonstrated sample transportation to the microfluidic device for electrochemical measurements, and could be readily adapted to accommodate different pre-processing steps. Overall, this study demonstrates the use of electrochemical sensors as part of an autonomous microfluidic handling system that would be functionally analogous to an electrochemical instrument designed for Ocean World exploration.

One of the highest science risks during NASA missions involving living organisms, including the search for them and/or their biomarkers or signatures, is the quality and reliability of sample preparation and handling prior to in-situ analysis (1; 2). Afluidic instrument is being developed, Charged Info-storage Polymer Prep System (ChIPPS), that will enable automated preparation of an environmental sample by extracting, concentrating, and desalting information-storage polymers. Linear charged polymers with multiple functional block types—typified by, though not limited to, the nucleic acids DNA and RNA— are a class of molecules understood to be necessary for life’s function and replication (3). The capability to characterize charged polymers for detecting biosignatures is driven by the emergence of nanopore technology. ChIPPS will prepare environmental samples for downstream delivery to biosignatures detection instruments, such as those being developed using nanopore technologies. References: (1) La Duc, M.T.et al."Comparative analysis of methods for the purification of DNA from low‐bio-mass samples based on total yield and conserved microbial diversity," JRapid Methods & Automation Microbio17.3(2009): 350-68. (2) Salmon, K.et al."Global gene expression profiling in Escherichia coliK12 the effects of oxy-gen availability and FNR," J.BioChem278.32(2003): 29837-55. (3) Benner, Steven A., and Daniel Hutter. "Phosphates, DNA, and the search for nonterrean life: A second generation model for genetic molecules," BioorgChem30.1(2002): 62-80

International audience; Motivated by the recent detection of chlorobenzene by the Sample Analysis at Mars instrument suite on the Curiosity rover, and the identification of its carbon source as indigenous to the martian sample, we reexamined the original, microfilm preserved, Viking gas chromatograph‐mass spectrometer (GCMS) data sets. We found evidence for the presence of chlorobenzene in Viking Lander 2 (VL‐2) data at levels corresponding to 0.08‐1.0 ppb (relative to sample mass), in runs when the sample was heated to 350°C and 500°C. Additionally, we found a correlation between the temperature dependence of the chlorobenzene signal and the dichloromethane signal originally identified by the Viking GCMS team. We considered possible sources of carbon that may have produced the chlorobenzene signal, by reaction with perchlorate during pyrolysis, including organic carbon indigenous to the martian parent sample and instrument contamination. We conclude that the chlorobenzene signal measured by VL‐2 originated from martian chlorine sources. We show how the carbon source could originate from the martian parent sample, though a carbon source contributed from instrument background cannot yet be ruled out.

Numerical models and measurements at the Martian surface show that ionizing radiation in the form of galactic cosmic rays and solar energetic particles impinging on the planet's surface and results in the formation of secondary ionizing radiation that affects the top dozen meters of the subsurface. In this brief review, we quantitatively model this secondary ionizing radiation as function of energy and depth. We then use basic physical arguments to explain the effect of this secondary ionization on organic molecules and cells and estimate microbe survival times as function of depth and soil type. Finally, we compare our calculated results on Deinococcus radiodurans survival time with other studies that have been reported in the literature.

We report results from the exposure of the metalloporphyrin iron tetraphenylporphyrin chloride (FeTPPCl) to the outer space environment, measured in situ aboard the Organism/Organic Exposure to Orbital Stresses nanosatellite. FeTPPCl was exposed for a period of 17 months (3700 h of direct solar exposure), which included broad-spectrum solar radiation (∼122 nm to the near infrared). Motivated by the potential role of metalloporphyrins as molecular biomarkers, the exposure of thin-film samples of FeTPPCl to the space environment in low-Earth orbit was monitored in situ via ultraviolet/visible spectroscopy and reported telemetrically. The space data were complemented by laboratory exposure experiments that used a high-fidelity solar simulator covering the spectral range of the spaceflight measurements. We found that thin-film samples of FeTPPCl that were in contact with a humid headspace gas (0.8-2.3% relative humidity) were particularly susceptible to destruction upon irradiation, degrading up to 10 times faster than identical thin films in contact with dry headspace gases; this degradation may also be related to the presence of oxides of nitrogen in those cells. In the companion terrestrial experiments, simulated solar exposure of FeTPPCl films in contact with either Ar or CO2:O2:Ar (10:0.01:1000) headspace gas resulted in growth of a band in the films' infrared spectra at 1961 cm(-1). We concluded that the most likely carriers of this band are allene (C3H4) and chloropropadiene (C3H3Cl), putative molecular fragments of the destruction of the porphyrin ring. The thin films studied in space and in solar simulator-based experiments show qualitatively similar spectral evolution as a function of contacting gaseous species but display significant differences in the time dependence of those changes. The relevance of our findings to planetary science, biomarker research, and the photostability of organic materials in astrobiologically relevant environments is discussed.

The O/OREOS (Organism/Organic Exposure to Orbital Stresses) nanosatellite is the first science demonstration spacecraft and flight mission of the NASA Astrobiology Small- Payloads Program (ASP). O/OREOS was launched successfully on November 19, 2010, to a high-inclination (72 deg), 650-km Earth orbit aboard a US Air Force Minotaur IV rocket from Kodiak, Alaska. O/OREOS consists of 3 conjoined cubesat (each 1000 cu cm) modules: (i) a control bus; (ii) the Space Environment Survivability of Living Organisms (SESLO) experiment; and (iii) the Space Environment Viability of Organics (SEVO) experiment. Among the innovative aspects of the O/OREOS mission are a real-time analysis of the photostability of organics and biomarkers and the collection of data on the survival and metabolic activity for microorganisms at 3 times during the 6-month mission. We report on the spacecraft characteristics, payload capabilities, and present operational phase and flight data from the O/OREOS mission. The science and technology rationale of O/OREOS supports NASA0s scientific exploration program by investigating the local space environment as well as space biology relevant to Moon and Mars missions. It also serves as a precursor for experiments on small satellites, the International Space Station (ISS), future free-flyers and lunar surface exposure facilities.

The measurement of the soluble properties (pH, eH, conductivity, specific ion concentrations, etc.) of planetary science samples provides important information on the habitability of a location, the bulk components of a sample, the potential for undesired effects on analysis protocols, and the history/preservation of the sample (e.g., geologic weathering, radiation processing, etc.). Electrochemical sensors are an ideal means to measure soluble properties because they excel at detecting ionic species in solution. The Wet Chemistry Lab (WCL) on the 2007 Mars Phoenix Lander was the first planetary science instrument to focus on soluble inorganic ion measurements and used an array of electrochemical sensors. WCL’s discovery of significant quantities of perchlorate salts in the Martian regolith helped reshape our understanding of Martian chemistry and the search for past or present life there. As NASA starts on a new chapter of exploration with potential missions to further out locations like the Ocean Worlds of Europa and Enceladus, it is a natural fit to adapt the successful WCL instrument for operation on bodies where the samples could be ice or liquid. Since the successful operation of WCL on Mars there have been a number of projects to improve sensor capabilities, develop microfluidic implementations, and prepare for Ocean World mission scenarios. This work has led to a number of developments, including: 1. Production of Ag/AgCl reference electrodes that are stable for use during flight missions. 2. Cyclic voltammetry methods for the specific detection of SO4 2- and NO3 -. 3. Adaptation of hydrogel-based ion-sensitive electrodes (ISEs) for use in microfluidic arrays. 4. The development of solid-contact ISEs for use during flight missions. 5. Radiation testing of ISE ionophores. 6. The development of microfluidic infrastructure based on successful small satellite payloads. The combination of all this work has led to a significant increase in sensor/system performance and robustness in preparation for potential missions to Ocean Worlds.

Biological redox is a promising indicator of life for NASA’s future exploration missions of Ocean Worlds. Electrochemical sensors are valuable tools for detecting these biological redox signatures on Earth; however their application to planetary exploration has been limited. All forms of life on Earth contain cellular machinery that can transform and regulate chemical energy through electron transfer pathways performed by key classes of naturally-occurring biological redox molecules including flavins, nicotinamides, porphyrins, and quinones. In this study, we use electrochemical techniques to measure these redox molecules in a synthetic seawater solution. This study also appropriates an electrochemical immunoassay technique for alkaline phosphatase detection, where comparison of the unique redox signatures of enzyme substrates and products reflect enzymatic activity. Naturally-occurring redox molecules exhibit unique redox signatures with anodic peak locations indicative of their respective molecular class. In this work, we report measured limits of detection as low as 10 nM and 3.13 aM for naturally-occurring redox molecules and alkaline phosphatase respectively. Overall, the findings of this study demonstrate that electrochemical sensors are effective tools for life detection applications for future Ocean Worlds missions.

Biomarkers collected from past and present life on Earth are a central guide in the development of flight-ready technologies designed to search for life on other planets and moons. Data from numerous laboratory and field studies have revealed the importance of incorporating capabilities that minimize the risk of false negatives or false positives during life detection missions. Biomolecules are the most unambiguous and information-rich of all known biosignatures. Indeed, the identification in a sample of biopolymers akin to DNA, RNA or proteins, would be difficult to refute as a successful life detection experiment. In the case of Mars, the search for biomolecules is inescapable, but few technological solutions exist for in situ identification. Thus, our work has focused on the development of technologies designed to detect biochemical polyelectrolyte molecules, which have been argued to be a universal signature for life due to their ability to store information while reducing their tendency to adopt complex tertiary structures that would prohibit their replication. To that end we have developed a solid-state nanopore device that has the ability to detect electrically charged organic polymers, such as those found in deoxyribonucleic acid. Our nanopore technology, when used as a biosensor, consists of two or three ion-filled chambers separated by voltage-biased thin layer (Figure 1). Nanopores are milled into the thin layer, allowing the chambers to be connected electrically via an ionic solution. Polyelectrolytes are introduced into one of the chambers, and a patch clamp amplifier is connected to the chip via electrodes that serve as a voltage source and an ammeter. When a voltage is applied across the membrane, the ionic current going only through this pore is measured. The polyelectrolytes are captured by the electric field in the pore, then and electrophoretically drawn through the nanopore (translocation) causing the nanopore conductance to decrease. This conductance decrease, or transient current blockage, is evaluated for: 1) mean blockage current (which is caused by the physical passage of the polyelectrolyte through the nanopore, and is measured by a sensitive ammeter in pA); 2) translocation duration (physical time of the translocation, for DNA this is typically 30 bases per second when translocation is controlled by a molecular motor [1]); and 3) integrated area of a blockage, revealing key features of the particle. Solid-state nanopore technology is being aggressively advanced for use as an electrochemistry sensor for a wide variety of biological molecules. Testing of the solid-state nanopore membranes includes the establishment of criteria used to distinguish informational from non-informational output signals. Our work highlights past, current, and future efforts in the development of solid-state nanopore technology for life detection. References: Deamer, D., M. Akeson, and D. Branton, Three decades of nanopore sequencing. Nature biotechnology, 2016. 34(5): p. 518. Acknowledgements: This project is supported by the NASA Research Opportunities in Space and Earth Sciences Program’s Concepts for Ocean worlds Life Detection Technology, Solicitation: NNH16ZDA001N-CLDTCH and the W.M. Keck Center for Nanoscale Optofluidics at UC Santa Cruz. Figure 1. The microfluidic chip with an integrated solid-state nanopore. (a) The Z-shaped microfluidic channel is shown in blue. Three fluidic reservoirs are used for buffer and analyte introduction into the microfluidic channel, with the nanopore integrated beneath the central chamber (number 2). During the experiment, analyte solution is introduced into the central chamber and voltage is applied across the microfluidic channel and nanopore. (b) SEM cross-section of the microfluidic channel with the integrated micropore and nanopore in the top layers of the chip. (c) Photograph of the assembled device. Figure 1

The search for evidence of life on Mars is the primary motivation for the exploration of that planet. The results from previous missions, and the Phoenix mission in particular, indicate that the ice-cemented ground in the north polar plains is likely to be the most recently habitable place that is currently known on Mars. The near-surface ice likely provided adequate water activity during periods of high obliquity, ≈ 5 Myr ago. Carbon dioxide and nitrogen are present in the atmosphere, and nitrates may be present in the soil. Perchlorate in the soil together with iron in basaltic rock provides a possible energy source for life. Furthermore, the presence of organics must once again be considered, as the results of the Viking GCMS are now suspect given the discovery of the thermally reactive perchlorate. Ground ice may provide a way to preserve organic molecules for extended periods of time, especially organic biomarkers. The Mars Icebreaker Life mission focuses on the following science goals: (1) Search for specific biomolecules that would be conclusive evidence of life. (2) Perform a general search for organic molecules in the ground ice. (3) Determine the processes of ground ice formation and the role of liquid water. (4) Understand the mechanical properties of the martian polar ice-cemented soil. (5) Assess the recent habitability of the environment with respect to required elements to support life, energy sources, and possible toxic elements. (6) Compare the elemental composition of the northern plains with midlatitude sites. The Icebreaker Life payload has been designed around the Phoenix spacecraft and is targeted to a site near the Phoenix landing site. However, the Icebreaker payload could be supported on other Mars landing systems. Preliminary studies of the SpaceX Dragon lander show that it could support the Icebreaker payload for a landing either at the Phoenix site or at midlatitudes. Duplicate samples could be cached as a target for possible return by a Mars Sample Return mission. If the samples were shown to contain organic biomarkers, interest in returning them to Earth would be high.

The hypothesis that bombardment of lunar soil with solar-wind protons might form hydroxyl (OH) and perhaps HOH has been tested by experiments with Apollo 16 (highlands) and Apollo 17 (mare) soils. Pre-dried soils (500 °C) were bombarded with 1.1 keV protons and deuterons and provide unambiguous evidence for the formation of OH or OD in both samples. This hypothesis further predicts the formation of hydroxyl (OH) on other airless planetary/asteroidal bodies, with a sufficient solar-wind flux. Deuteron implantation of unaltered lunar soils and a heat-treated plagioclase specimen cause simultaneous OH depletion and OD formation. Ion bombardment of lunar soils simulates the dynamic process of hydroxyl formation and may also deplete intrinsic OH, thereby effectively contributing to the day/night, diurnal variability of OH reported by Sunshine et al. (2009) . Our results emphasize the need to use lunar soils with space-weathered exteriors in laboratory simulations of the solar wind. Infrared spectra of hydrogen ion-beam implanted soils are similar to spectra obtained at RELAB (Brown Univ.) and to those observed by remote sensing confirming the solar-wind hypothesis.

The Space Environment Viability of Organics (SEVO) experiment is one of two scientific payloads aboard the triple-cube satellite Organism/ORganic Exposure to Orbital Stresses (O/OREOS). O/OREOS is the first technology demonstration mission of the NASA Astrobiology Small Payloads Program. The 1-kg, 1000-cm3 SEVO cube is investigating the chemical evolution of organic materials in interstellar space and planetary environments by exposing organic molecules under controlled conditions directly to the low-Earth orbit (LEO) particle and electromagnetic radiation environment. O/OREOS was launched on November 19, 2010 into a 650-km, 72°-inclination orbit and has a nominal operational lifetime of six months. Four classes of organic compounds, namely an amino acid, a quinone, a polycyclic aromatic hydrocarbon (PAH), and a metallo-porphyrin are being studied. Initial reaction conditions were established by hermetically sealing the thin-film organic samples in self-contained micro-environments. Chemical changes in the samples caused by direct exposure to LEO radiation and by interactions with the irradiated microenvironments are monitored in situ by ultraviolet/visible/near-infrared (UV/VIS/NIR) absorption spectroscopy using a novel compact fixed-grating CCD spectrometer with the Sun as its light source. The goals of the O/OREOS mission include: (1) demonstrating key small satellite technologies that can enable future low-cost astrobiology experiments, (2) deploying a miniature UV/VIS/NIR spectrometer suitable for in-situ astrobiology and other scientific investigations, (3) testing the capability to establish a variety of experimental reaction conditions to enable the study of astrobiological processes on small satellites, and (4) measuring the chemical evolution of organic molecules in LEO under conditions that can be extrapolated to interstellar and planetary environments. In this paper, the science and technology development of the SEVO instrument payload and its measurements are described.

2018 marks the 10-year anniversary of the landing of the NASA Phoenix spacecraft on the ice-rich northern plains of Mars. The Phoenix Lander carried the Wet Chemistry Laboratory (WCL), a component instrument of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) and was used to perform a comprehensive electrochemical characterization of martian soil in an aqueous solution. Designed to characterize the habitability of the martian surface, WCL contained an array of ion selective electrodes, a conductivity cell, a platinum electrode to measure redox potential, electrodes to perform perform cyclic voltammetry, chronopotentiometry and anodic stripping voltammetry, as well as a set of chemical reagents used to perform a sulfate titration and sample acidification. The measurements made with WCL resulted in a number of major discoveries, including the detection of percent levels of perchlorate on the martian surface, and represent the first, and to date, the only time electrochemical methods have been used for planetary exploration beyond Earth. NASA is now embarking on a new era of astrobiology exploration as plans are being formulated for missions to Ocean Worlds of the outer solar system, including Europa, an ice covered Jovian moon. Based on lessons learned during the development of WCL and its operation on the surface of Mars, we will discuss new design approaches and strategies that will enable the implementation of autonomous microfluidic electrochemical sensor arrays during upcoming missions to these yet to be explored solar system environments.

Life on Earth is one of the outcomes of the formation and evolution of our solar system and has adapted to every explored environment on planet Earth. Recent discoveries have shown that life can exist in extreme environments, such as hydrothermal vents, in deserts and in ice lakes in Antarctica. These findings challenge the definition of the ' planetary habitable zone '. The objective of future international planetary exploration programmes is to implement a long-term plan for the robotic and human exploration of solar system bodies. Mars has been a central object of interest in the context of extraterrestrial life. The search for extinct or extant life on Mars is one of the main goals of space missions to the Red Planet during the next decade. In this paper we describe the investigation of the physical and chemical properties of Mars soil analogues collected in arid deserts. We measure the pH, redox potential and ion concentrations, as well as carbon and amino acid abundances of soils collected from the Atacama desert (Chile and Peru) and the Salten Skov sediment from Denmark. The samples show large differences in their measured properties, even when taken only several meters apart. A desert sample and the Salten Skov sediment were exposed to a simulated Mars environment to test the stability of amino acids in the soils. The presented laboratory and field studies provide limits to exobiological models, evidence on the effects of subsurface mineral matrices, support current and planned space missions and address planetary protection issues. Received 15 April 2009, accepted 18 June 2009, first published online 30 July 2009

Phoenix Ascending The Phoenix mission landed on Mars in March 2008 with the goal of studying the ice-rich soil of the planet's northern arctic region. Phoenix included a robotic arm, with a camera attached to it, with the capacity to excavate through the soil to the ice layer beneath it, scoop up soil and water ice samples, and deliver them to a combination of other instruments—including a wet chemistry lab and a high-temperature oven combined with a mass spectrometer—for chemical and geological analysis. Using this setup, Smith et al. (p. 58 ) found a layer of ice at depths of 5 to 15 centimeters, Boynton et al. (p. 61 ) found evidence for the presence of calcium carbonate in the soil, and Hecht et al. (p. 64 ) found that most of the soluble chlorine at the surface is in the form of perchlorate. Together these results suggest that the soil at the Phoenix landing site must have suffered alteration through the action of liquid water in geologically the recent past. The analysis revealed an alkaline environment, in contrast to that found by the Mars Exploration Rovers, indicating that many different environments have existed on Mars. Phoenix also carried a lidar, an instrument that sends laser light upward into the atmosphere and detects the light scattered back by clouds and dust. An analysis of the data by Whiteway et al. (p. 68 ) showed that clouds of ice crystals that precipitated back to the surface formed on a daily basis, providing a mechanism to place ice at the surface.

Phoenix Ascending The Phoenix mission landed on Mars in March 2008 with the goal of studying the ice-rich soil of the planet's northern arctic region. Phoenix included a robotic arm, with a camera attached to it, with the capacity to excavate through the soil to the ice layer beneath it, scoop up soil and water ice samples, and deliver them to a combination of other instruments—including a wet chemistry lab and a high-temperature oven combined with a mass spectrometer—for chemical and geological analysis. Using this setup, Smith et al. (p. 58 ) found a layer of ice at depths of 5 to 15 centimeters, Boynton et al. (p. 61 ) found evidence for the presence of calcium carbonate in the soil, and Hecht et al. (p. 64 ) found that most of the soluble chlorine at the surface is in the form of perchlorate. Together these results suggest that the soil at the Phoenix landing site must have suffered alteration through the action of liquid water in geologically the recent past. The analysis revealed an alkaline environment, in contrast to that found by the Mars Exploration Rovers, indicating that many different environments have existed on Mars. Phoenix also carried a lidar, an instrument that sends laser light upward into the atmosphere and detects the light scattered back by clouds and dust. An analysis of the data by Whiteway et al. (p. 68 ) showed that clouds of ice crystals that precipitated back to the surface formed on a daily basis, providing a mechanism to place ice at the surface.

Carbonates, predominately MgCO3, have been spectroscopically identified at a level of 2-5% in martian dust. However, in spite of this observation, and a large number of climate studies that suggest 1 to several bars of CO2 should be sequestered in carbonate rocks, no outcrop-scale exposures of carbonate have been detected anywhere on Mars to date. To address one hypothesis for this long-standing puzzle, the effect of ultraviolet (UV) light on the stability of calcium carbonate in a simulated martian atmosphere was experimentally investigated. Using 13C-labeled calcite, we found no experimental evidence of the UV photodecomposition of calcium carbonate in a simulated martian atmosphere. Extrapolating the lower limit of detection of our experimental system to an upper limit of carbonate decomposition on Mars yields a quantum efficiency of 3.5 x 10(-8) molecules/photon over the wavelength interval of 190-390 nm and a maximum UV photodecomposition rate of 1.2 x 10(-13) kg m(-2) s(-1) from a calcite surface. The maximum loss of bulk calcite due to this process would be 2.5 nm year(-1) (Mars year). However, calcite is expected to be thermodynamically stable on the surface of Mars, and potential UV photodecomposition reaction mechanisms indicate that, though calcium carbonate may decompose under vacuum, it would be stable in a CO2 atmosphere. Given the expected stability of carbonate on Mars and our inability to detect carbonate decomposition, we conclude that it is unlikely that the apparent absence of extensive carbonate deposits on the martian surface is due to UV photodecomposition in the current environment.

We describe an atmospheric oxidation sensor developed and delivered as part of the European Space Agency (ESA) Beagle 2 (B2) Mars Lander Environmental Sensor Suite (ESS). The sensor monitors atmospheric oxidation rates by measuring resistance changes in a thin-silver (Ag) film deposited in situ onto a sapphire substrate while on the surface of Mars. Potential terrestrial applications of this sensing approach include long-term monitoring of oxidative contaminants in low-oxygen systems including process gases and environmental chambers. The sensor response to ppb levels of hydrogen peroxide (H2O2) vapor in carbon dioxide (CO2) is demonstrated.

Hydrated magnesium sulfate salts have been proposed as major components of the disrupted, reddish terrains on the surface of Europa. This is based on near-infrared reflectance spectra which contain distorted and asymmetric water absorption features typical of moderately hydrated materials such as hexahydrite (MgSO4⋅6H2O) and epsomite (MgSO4⋅7H2O). Hydrated magnesium sulfates having many waters of hydration could produce improved spectral matches. Here we present cryogenic laboratory spectra of highly hydrated sulfur-bearing salts, including hexahydrite, epsomite, bloedite (Na2Mg(SO4)2⋅4H2O), mirabilite (Na2SO4⋅10H2O), sodium sulfide nonahydrate (Na2S⋅9H2O), supersaturated MgSO4, NaHCO3, and Na2SO4 brines, and magnesium sulfate dodecahydrate (MgSO4⋅12H2O). All have been measured under conditions of pressure and temperature appropriate to the surface environment of Europa. Novel methods for preparation, verification and analysis of MgSO4⋅12H2O, which is not stable at standard temperature and pressure (STP), are described. At 100 K, all of these materials exhibit distorted and asymmetric absorption features similar to those in the Europa observations, as well as several weaker, narrow absorptions having widths ranging from 15 to 80 nm. While the agreement with Galileo NIMS observations of dark terrains on Europa is indeed better for highly hydrated salts than for salts of lower hydration states, we conclude that none of these materials alone can account for all of the observed spectral character. As previously suggested, Europa's reddish material appears to be a complex mixture of sulfate hydrates and other materials.

In the framework of international planetary exploration programs, several space missions are planned to search for organics and bio-signatures on Mars. Previous attempts have not detected any organic compounds in the Martian regolith. It is therefore critical to investigate the processes that may affect organic molecules on and below the planet's surface. Laboratory simulations can provide useful data about the reaction pathways of organic material at Mars' surface. We have studied the stability of amino acid thin films against ultraviolet (UV) irradiation and use those data to predict the survival time of these compounds on and in the Martian regolith. We show that thin films of glycine and D-alanine are expected to have half-lives of 22 ± 5 hr and of 3 ± 1 hr, respectively, when irradiated with Mars-like UV flux levels. Modelling shows that the half-lives of the amino acids are extended to the order of 10 7 years when embedded in regolith. These data suggest that subsurface sampling must be a key component of future missions to Mars dedicated to organic detection.

A suite of instruments on the Beagle 2 Mars lander was designed and built in order to investigate the environmental conditions at the landing site. The sensor suite was capable of measuring air temperature at two heights, surface level pressure, wind speed and direction, saltated particle momentum, UV flux (diffuse and direct at five wavelengths), the total accumulated radiation dose and investigating the nature of the oxidising environment. The scientific goals of the instruments are discussed within the context of current understanding of the environmental conditions on Mars, and the instruments themselves are described in detail. Beagle 2 landed on Mars in late 2003, as part of the ESA Mars Express mission. The expected lifetime of the lander on the surface was 180 sols, with a landing site in Isidis Planitia, but has not responded to attempts to contact it, and has now been declared lost. The Environmental Sensor Suite (ESS) was intended to monitor and characterise the current local meteorological parameters, investigating specific areas of scientific interest raised from previous missions, most notably dust transport and transient phenomena, and additionally to add context to the conditions that any possible martian micro-organisms would have to face. The design of the instrument suite was strongly influenced by mass limitations, with eight sensor subsystems having a total mass of approximately 100g. Although Beagle 2 has been now declared lost, the scientific goals of an Environmental Sensors Suite still remain a valid target for any future astrobiology orientated missions. © 2004 Elsevier Ltd. All rights reserved.

In this report, we show controlled in-situ doping of a single crystalline metal oxide nanowire, using indium-doped tin oxide (In−SnO2) as an example, during a heteroepitaxial growth process. Highly regular and high-density arrays of In−SnO2 nanowires, which demonstrate three- and four-fold growth symmetry, are obtained directly on optical sapphire substrates. Similar synthesis strategies, involving careful selection of desired growth conditions and smart manipulation of favorable thermodynamic properties, could be extended to production of various doped metal oxide nanowires.

We describe a chemometric array sensor, the Mars Atmospheric Oxidant Sensor (MAOS, pronounced "mouse '') that is designed measure the oxidation rate of thin films on the martian surface. We select films that are sensitive to particular types of oxidants, that represent key elements in the martian soil, or that emulate prebiotic materials. Concern that naturally arising martian oxidants may have destroyed evidence of ancient life on Mars was raised by the Viking mission in the 1970's. The possibility that oxidants may limit the viability of biologica1 habitats is particularly timely in light of recent suggestions of contemporary flowing water on Mars. By controlling the temperature of the films, as well as their exposure to dust and ultraviolet light, MAOS will discriminate among leading hypotheses for oxidant production. MAOS weighs 55 grams, fits in a 6 x 7 x 2 cm envelope, and uses 250 mW power. Much of the enabling technology was developed for the MOx experiment, lost on the Russian Mars '96 mission.

The OREOcube (ORganics Exposure in Orbit cube) experiment on the International Space Station (ISS) will investigate the effects of solar and cosmic radiation on organic thin films supported on inorganic substrates. Probing the kinetics of structural changes and photomodulated organic-inorganic interactions with real-time in situ UV-visible spectroscopy, this experiment will investigate the role played by solid mineral surfaces in the (photo)chemical evolution, transport, and distribution of organics in our solar system and beyond. In preparation for the OREOcube ISS experiment, we report here laboratory measurements of the photostability of thin films of the 9,10-anthraquinone derivative anthrarufin (51 nm thick) layered upon ultrathin films of iron oxides magnetite and hematite (4 nm thick), as well as supported directly on fused silica. During irradiation with UV and visible light simulating the photon flux and spectral distribution on the surface of Mars, anthrarufin/iron oxide bilayer thin films were exposed to CO2 (800 Pa), the main constituent (and pressure) of the martian atmosphere. The time-dependent photodegradation of anthrarufin thin films revealed the inhibition of degradation by both types of underlying iron oxides relative to anthrarufin on bare fused silica. Interactions between the organic and inorganic thin films, apparent in spectral shifts of the anthrarufin bands, are consistent with presumed free-electron quenching of semiquinone anion radicals by the iron oxide layers, effectively protecting the organic compound from photodegradation. Combining such in situ real-time kinetic measurements of thin films in future space exposure experiments on the ISS with postflight sample return and analysis will provide time-course studies complemented by in-depth chemical analysis. This will facilitate the characterization and modeling of the chemistry of organic species associated with mineral surfaces in astrobiological contexts.

Using a validated general circulation model, we determine where and for how long the surface pressure and surface temperature on Mars meet the minimum requirements for the existence of liquid water in the present climate system: pressures and temperatures above the triple point of water but below the boiling point. We find that for pure liquid water, there are five “favorable” regions where these requirements are satisfied: between 0° and 30°N in the plains of Amazonis, Arabia, and Elysium; and in the Southern Hemisphere impact basins of Hellas and Argyre. The combined area of these regions represents 29% of the planet's surface area. In the Amazonis region these requirements are satisfied for a total integrated time of 37 sols each Martian year. In the Hellas basin the number of degree days above zero is 70, which is well above those experienced in the dry valley lake region of Antarctica. These regions are remarkably well correlated with the location of Amazonian paleolakes mapped by Cabrol and Grin [2000] but are poorly correlated with the seepage gullies found by Malin and Edgett [2000]. In both instances, obliquity variations may play a role. For brine solutions the favorable regions expand and could potentially include most of the planet for highly concentrated solutions. Whether liquid water ever forms in these regions depends on the availability of ice and heat and on the evaporation rate. The latter is poorly understood for low-pressure CO2 environments but is likely to be so high that melting occurs rarely, if at all. However, even rare events of liquid water formation would be significant since they would dominate the chemistry of the soil and would have biological implications as well. It is therefore worth reassessing the potential for liquid water formation on present day Mars, particularly in light of recent Mars Global Surveyor observations.

Hydrogen peroxide chemisorbed on titanium dioxide (peroxide-modified titanium dioxide) is investigated as a chemical analog to the putative soil oxidants responsible for the chemical reactivity seen in the Viking biology experiments. When peroxide-modified titanium dioxide (anatase) was exposed to a solution similar to the Viking labeled release (LR) experiment organic medium, CO2 gas was released into the sample cell headspace. Storage of these samples at 10 degrees C for 48 hr prior to exposure to organics resulted in a positive response while storage for 7 days did not. In the Viking LR experiment, storage of the Martian surface samples for 2 sols (approximately 49 hr) resulted in a positive response while storage for 141 sols essentially eliminated the initial rapid release of CO2. Heating the peroxide-modified titanium dioxide to 50 degrees C prior to exposure to organics resulted in a negative response. This is similar to, but not identical to, the Viking samples where heating to approximately 46 degrees C diminished the response by 54-80% and heating to 51.5 apparently eliminated the response. When exposed to water vapor, the peroxide-modified titanium dioxide samples release O2 in a manner similar to the release seen in the Viking gas exchange experiment (GEx). Reactivity is retained upon heating at 50 degrees C for three hours, distinguishing this active agent from the one responsible for the release of CO2 from aqueous organics. The release of CO2 by the peroxide-modified titanium dioxide is attributed to the decomposition of organics by outer-sphere peroxide complexes associated with surface hydroxyl groups, while the release of O2 upon humidification is attributed to more stable inner-sphere peroxide complexes associated with Ti4+ cations. Heating the peroxide-modified titanium dioxide to 145 degrees C inhibited the release of O2, while in the Viking experiments heating to this temperature diminished but did not eliminated the response. Although the thermal stability of the titanium-peroxide complexes in this work is lower than the stability seen in the Viking experiments, it is expected that similar types of complexes will form in titanium containing minerals other than anatase and the stability of these complexes will vary with surface hydroxylation and mineralogy.

We describe the development of a thermoacoustic oxidant sensor (TAOS) array to quantify gases that play critical roles in the chemical evolution of the martian surface and atmosphere. The sensor combines a chemiresistor with an acoustic wave-plate device, micro-fabricated on thermally isolated hot-plates; their measurement modes are respectively: conductivity changes of chemically sensitive films, and mass changes of the same coatings. Metal Phthalocyanines (MePcs) and other organic semiconductors such as 1,4-polybutadiene are used as chemical coatings because of their chemical stability and the fact that these compounds have been shown to exhibit selectivity to oxidizing gases. The specific target gases of this experiment are H2O2, H2O, O3 and CO. Identification and quantification of these gases at the martian surface would contribute to both atmospheric and soil chemistry studies. The species H2O2 and/or O3, may be responsible for the unique reactive properties of the martian regolith, as discovered in the Viking biology experiments. In addition, each of the target gases are believed to play a role in the photochemical recycling of CO2.

New measurements of the adsorption of H2O onto terrestrial materials, under Mars-like conditions, disagree with predictions made on the basis of the most frequently used adsorption isotherms. We report here on additional measurements, which confirm that previous estimates of H2O adsorptive coverage of Martian surface minerals were too high. This discrepancy is a result of extrapolating an empirical expression for adsorption that can be shown to contain unrealistic assumptions. New isotherms, developed to describe adsorption on heterogeneous surfaces, are well suited to describing adsorption at Mars-like conditions. The new isotherms predict that the adsorptive capacity of the regolith is lower than previously thought, if normalized for available surface area. The adsorptive behavior of the regolith materials, to first order, can be predicted on the basis of their specific surface area, without regard to composition. For a given specific surface area of a few tens of square meters per gram, we show that vapor diffusion is more rapid, and that predawn, near-surface ground ice must occur more commonly than previously thought. We find that the presence of a few percent of smectites in the upper few centimeters of the regolith can dominate the adsorption cycle.

Results from the Viking biology experiments indicate the presence of reactive oxidants in martian soils that have previously been attributed to peroxide and superoxide. Instruments on the Mars Phoenix Lander and the Mars Science Laboratory detected perchlorate in martian soil, which is nonreactive under the conditions of the Viking biology experiments. We show that calcium perchlorate exposed to gamma rays decomposes in a CO2 atmosphere to form hypochlorite (ClO−), trapped oxygen (O2), and chlorine dioxide (ClO2). Our results show that the release of trapped O2 (g) from radiation-damaged perchlorate salts and the reaction of ClO− with amino acids that were added to the martian soils can explain the results of the Viking biology experiments. We conclude that neither hydrogen peroxide nor superoxide is required to explain the results of the Viking biology experiments. Key Words: Mars—Radiolysis—Organic degradation—in situ measurement—Planetary habitability and biosignatures. Astrobiology 13, 515–520.

We report the first science results from the Space Environment Viability of Organics (SEVO) payload aboard the Organism/Organic Exposure to Orbital Stresses (O/OREOS) free-flying nanosatellite, which completed its nominal spaceflight mission in May 2011 but continues to acquire data biweekly. The SEVO payload integrates a compact UV-visible-NIR spectrometer, utilizing the Sun as its light source, with a 24-cell sample carousel that houses four classes of vacuum-deposited organic thin films: polycyclic aromatic hydrocarbon (PAH), amino acid, metalloporphyrin, and quinone. The organic films are enclosed in hermetically sealed sample cells that contain one of four astrobiologically relevant microenvironments. Results are reported in this paper for the first 309 days of the mission, during which the samples were exposed for ∼2210 h to direct solar illumination (∼1080 kJ/cm(2) of solar energy over the 124-2600 nm range). Transmission spectra (200-1000 nm) were recorded for each film, at first daily and subsequently every 15 days, along with a solar spectrum and the dark response of the detector array. Results presented here include eight preflight and 16 in-flight spectra of eight SEVO sample cells. Spectra from the PAH thin film in a water-vapor-containing microenvironment indicate measurable change due to solar irradiation in orbit, while three other nominally water-free microenvironments show no appreciable change. The quinone anthrarufin showed high photostability and no significant spectroscopically measurable change in any of the four microenvironments during the same period. The SEVO experiment provides the first in situ real-time analysis of the photostability of organic compounds and biomarkers in orbit.

[1] Simulated Thermal Evolved Gas Analyzer (TEGA) analyses have shown that a CO2 release detected between 400°C and 680°C by the Phoenix Lander's TEGA instrument may have been caused by a reaction between calcium carbonate and hydrated magnesium perchlorate. In our experiments a CO2release beginning at 385 ± 12°C was attributed to calcite reacting with water vapor and HCl gas from the dehydration and thermal decomposition of Mg-perchlorate. The release of CO2 is consistent with the TEGA detection of CO2 released between 400 and 680°C, with the amount of CO2increasing linearly with added perchlorate. X-ray diffraction (XRD) experiments confirmed CaCl2 formation from the reaction between calcite and HCl. These results have important implications for the Mars Science Laboratory (MSL) Curiosity rover. Heating soils may cause inorganic release of CO2; therefore, detection of organic fragments, not CO2 alone, should be used as definitive evidence for organics in Martian soils.

[1] Results from the Mars Phoenix mission Wet Chemistry Laboratory (WCL) are used to determine the oxidation-reduction potential (Eh) of the Phoenix WCL Rosy Red sample soil solution. The measured Eh of the Rosy Red sample in the WCL aqueous test solution was 253 ± 6 mV at a pH of 7.7 ± 0.1. Measured solution Eh changes correspond to changes in solution H+ activity, which is controlled mainly by changes in headspace PCO2 and solution CO32−, HCO3−, and CO2 concentrations. If measured at a PCO2 of 8 mbar in water, rather than in WCL test solution, the Eh of the Rosy Red soil solution would be ∼300 mV. The results of laboratory experiments using analog salt mixtures are compatible with the possible presence of low levels (ppm) of metal peroxides or other oxidants and indicate that levels of readily soluble ferrous iron in the soil are below 1 ppm.

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.