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The question "Are we alone in the Universe?" is perhaps the most fundamental one that affects mankind. How can we address the search for life in our Solar System? Mars, Enceladus and Europa are the focus of the search for life outside the terrestrial biosphere. While it is more likely to find remnants of life (fossils of extinct life) on Mars because of its past short time window of the surface habitability, it is probably more likely to find traces of extant life on the icy moons and ocean worlds of Jupiter and Saturn. Nevertheless, even on Mars there could still be a chance to find extant life in niches near to the surface or in just discovered subglacial lakes beneath the South Pole ice cap. Here, the different approaches for the detection of traces of life in the form of biosignatures including pre-biotic molecules will be presented. We will outline the required infrastructure for this enterprise and give examples of future mission concepts to investigate the presence of life on other planets and moons. Finally, we will provide suggestions on methods, techniques, operations and strategies for preparation and realization of future life detection missions.

The weathering of volcanic rocks contributes significantly to the global silicate weathering budget, effecting carbon dioxide drawdown and long-term climate control. The rate of chemical weathering is influenced by the composition of the rock. Rock-dwelling micro-organisms are known to play a role in changing the rate of weathering reactions; however, the influence of rock composition on bio-weathering is unknown. Cyanobacteria are known to be a ubiquitous surface taxon in volcanic rocks. In this study, we used a selection of fast and slow growing cyanobacterial species to compare microbial-mediated weathering of bulk crystalline rocks of basaltic and rhyolitic composition, under batch conditions. Cyanobacterial growth caused an increase in the pH of the medium and an acceleration of rock dissolution compared to the abiotic controls. For example, Anabaena cylindrica increased the linear release rate (R i l) of Ca, Mg, Si and K from the basalt by more than fivefold (5.21-12.48) and increased the pH of the medium by 1.9 units. Although A. cylindrica enhanced rhyolite weathering, the increase in R i l was less than threefold (2.04-2.97) and the pH increase was only 0.83 units. The R i l values obtained with A. cylindrica were at least ninefold greater with the basalt than the rhyolite, whereas in the abiotic controls, the difference was less than fivefold. Factors accounting for the slower rate of rhyolite weathering and lower biomass achieved are likely to include the higher content of quartz, which has a low rate of weathering and lower concentrations of bio-essential elements, such as, Ca, Fe and Mg, which are known to be important in controlling cyanobacterial growth. We show that at conditions where weathering is favoured, biota can enhance the difference between low and high Si-rock weathering. Our data show that cyanobacteria can play a significant role in enhancing rock weathering and likely have done since they evolved on the early Earth. © 2012 Blackwell Publ

Recent discoveries related to the habitability and astrobiological relevance of the outer Solar System have expanded our understanding of where and how life may have originated. As a result, the Icy Worlds of the outer Solar System have become among the highest priority targets for future spacecraft missions dedicated to astrobiology-focused and/or direct life detection objectives. This, in turn, has led to a renewed interest in planetary protection concerns and policies for the exploration of these worlds and has been a topic of discussion within the COSPAR (Committee on Space Research) Panel on Planetary Protection. This paper summarizes the results of those discussions, reviewing the current knowledge and the history of planetary protection considerations for Icy Worlds as well as suggesting ways forward. Based on those discussions, we therefore suggest to (1) Establish a new definition for Icy Worlds for Planetary Protection that captures the outer Solar System moons and dwarf planets like Pluto, but excludes more primitive bodies such as comets, centaurs, and asteroids: Icy Worlds in our Solar System are defined as all bodies with an outermost layer that is believed to be greater than 50% water ice by volume and have enough mass to assume a nearly round shape. (2) Establish indices for the lower limits of Earth life with regards to water activity (LLAw) and temperature (LLT) and apply them into all areas of the COSPAR Planetary Protection Policy. These values are currently set at 0.5 and -28°C and were originally established for defining Mars Special Regions; (3) Establish LLT as a parameter to assign categorization for Icy Worlds missions. The suggested categorization will have a 1000-year period of biological exploration, to be applied to all Icy Worlds and not just Europa and Enceladus as is currently the case. (4) Have all missions consider the possibility of impact. Transient thermal anomalies caused by impact would be acceptable so long as there i

Though Raman bands of α-amino acids (AA) are well documented, often only the strongest intensity bands are quoted as identifiers (e.g. Jenkins et al., 2005; De Gelder et al., 2007; Zhu et al., 2011). Unknown regolith mixtures on Mars-sampling missions could obscure these bands. Here the case is made for determining, via a statistical method, sets of characteristic bands to be used as identifiers, independent of band intensity or number of bands (Rolfe et al., 2016). AA have upwards of 25 potentially identifying bands and this method defines sets of 10–19 bands per AA. Examination of AA-doped Mars-like basalt resulted in a maximum of eight bands being identified, as some characteristic bands were obscured by mineral bands, including the strongest intensity band in some cases. This proved the need for characteristic bands to be defined, enabling successful identification of AA. The ESA ExoMars Rover mission will crush and then pass the sample to the Raman Laser Spectrometer. We crushed a Mars-like basalt to a similar grain size expected to be created by the rover. Our samples were doped with 1 % (by weight) AA samples, resulting in no detection of AA, because of loss of original spatial context and spaces between the grains. We recommend that Raman spectroscopy on future missions should be conducted before the sample is crushed. Halite-entombed halophilic microbes, known to survive being entombed, were exposed to Mars-like surface (including temperature, pressure, atmospheric composition and UV) and freeze-thaw cycle (plus pressure and atmospheric composition) conditions. This test on the survival of the microbes showed that survival rates quickly deteriorated in surface conditions, but freeze-thaw cycle samples had well preserved Raman biosignatures, indicating that similar signatures could be detectable on Mars if similar life persists in evaporitic material or brines today.

Biomarker molecules, such as amino acids, are key to discovering whether life exists elsewhere in the Solar System. Raman spectroscopy, a technique capable of detecting biomarkers, will be on board future planetary missions including the ExoMars rover. Generally, the position of the strongest band in the spectra of amino acids is reported as the identifying band. However, for an unknown sample, it is desirable to define multiple characteristic bands for molecules to avoid any ambiguous identification. To date, there has been no definition of multiple characteristic bands for amino acids of interest to astrobiology. This study examinedL-alanine, L-aspartic acid, L-cysteine, L-glutamine and glycine and defined several Raman bands per molecule for reference as characteristic identifiers. Per amino acid, 240 spectra were recorded and compared using established statistical tests including ANOVA. The number of characteristic bands defined were 10, 12, 12, 14 and 19 for L-alanine (strongest intensity band: 832 cm-1), L-aspartic acid (938 cm-1), L-cysteine (679 cm-1),L-glutamine (1090 cm−1) and glycine (875 cm-1), respectively. The intensity of bands differed by up to six times when several points on the crystal sample were rotated through 360 °; to reduce this effect when defining characteristic bands for other molecules, we find that spectra should be recorded at a statistically significant number of points per sample to remove the effect of sample rotation. It is crucial that sets of characteristic Raman bands are defined for biomarkers that are targets for future planetary missions to ensure a positive identification can be made.

Finding evidence of life elsewhere in the Solar System is dependent on understanding biotic processes that could occur within potentially habitable environments. Here, we describe a suite of high-pressure flow-through chambers that have been developed to investigate biotic and abiotic processes within simulated sub-surface martian and icy moon environments.

The transition of the martian climate from the wet Noachian era to the dry Hesperian (4.1–3.0 Gya) likely resulted in saline surface waters that were rich in sulfur species. Terrestrial analogue environments that possess a similar chemistry to these proposed waters can be used to develop an understanding of the diversity of microorganisms that could have persisted on Mars under such conditions. Here, we report on the chemistry and microbial community of the highly reducing sediment of Colour Peak springs, a sulfidic and saline spring system located within the Canadian High Arctic. DNA and cDNA 16S rRNA gene profiling demonstrated that the microbial community was dominated by sulfur oxidising bacteria, suggesting that primary production in the sediment was driven by chemolithoautotrophic sulfur oxidation. It is possible that the sulfur oxidising bacteria also supported the persistence of the additional taxa. Gibbs energy values calculated for the brines, based on the chemistry of Gale crater, suggested that the oxidation of reduced sulfur species was an energetically viable metabolism for life on early Mars

The Dallol volcano and its associated hydrothermal field are located in a remote area of the northern Danakil Depression in Ethiopia, a region only recently appraised after decades of inaccessibility due to severe political instability and the absence of infrastructure. The region is notable for hosting environments at the very edge of natural physical-chemical extremities. It is surrounded by a wide, hyperarid salt plain and is one of the hottest (average annual temperatureDallol: 36–38°C) and most acidic natural system (pHDallol ≈0) on Earth. Spectacular geomorphologies and mineral deposits produced by supersaturated hydrothermal waters and brines are the result of complex interactions between active and inactive hydrothermal alteration of the bedrock, sulfuric hot springs and pools, fumaroles and geysers, and recrystallization processes driven by hydrothermal waters, degassing, and rapid evaporation. The study of planetary field analog environments plays a crucial role in characterizing the physical and chemical boundaries within which life can exist on Earth and other planets. It is essential for the definition and assessment of the conditions of habitability on other planets, including the possibility for biosignature preservation and in situ testing of technologies for life detection. The Dallol area represents an excellent Mars analog environment given that the active volcanic environment, the associated diffuse hydrothermalism and hydrothermal alteration, and the vast acidic sulfate deposits are reminiscent of past hydrothermal activity on Mars. The work presented in this paper is an overview of the Dallol volcanic area and its hydrothermal field that integrates previous literature with observations and results obtained from field surveys and monitoring coupled with sample characterization. In so doing, we highlight its exceptional potential as a planetary field analog as well as a site for future astrobiologica

The draft genomes of the nitrate-dependent iron-oxidizing bacteria Acidovorax sp. strain BoFeN1 and Paracoccus pantotrophus strain KS1 are presented. These genomes supply supporting data to investigations of the mechanisms underlying this anaerobic form of microbial biogeochemical iron cycling.

Recent discoveries have reopened the idea that, in the past, Mars had a period of wetness where conditions were similar to those on Earth [1]. If this was the case then it is feasible that these environments may have harboured life. The martian surface today is dry, cold and heavily bombarded by UV radiation, making it an environment unsuitable for any known terrestrial life [2]; the martian subsurface might be considerably more hospitable. Subsurface microbial communities would not have access to sunlight for photosynthesis to drive their food chains, so primary production would have to be driven by chemolithoautotrophic organisms. Every successful Mars landing site has been found to have abundant surface salt [3], and halite has been detected in Martian meteorites [4]. While subsurface halite deposits have not yet been detected on Mars, areas on the surface consisting of unidentified chlorine deposits have been detected with evaporation as one of the main theories to explain their creation [5]. On Earth, chloride evaporites are home to halophiles, and they have been suggested as an analogue for potential Martian life. Halophiles are micro-organisms which display a high salt tolerance. Despite being found in evaporite deposits, they are normally studied in surface brines. Brines form when the rate of evaporation of water is greater than the rate that water enters an area [6], so eventually most brines evaporate and form salt crystals. Halophiles in a brine are able to alter the size and formation rate of fluid inclusions within these salt crystals so as to entomb themselves inside until the crystals can re-dissolve [7]. It is uncertain how long halophiles can spend entombed within crystals, but there are some who speculate that it could be up to millions of years, if not longer [8]. If life had arisen on Mars during an earlier, more hospitable, wet period, as it did on Earth, then when the planet cooled, organisms analogous to terrestrial halophiles might have had

The present day martian surface is cold, dry, exposed to UV radiation and bombarded with heavy ions [1]. Any remaining water in the near subsurface is likely to have a high salt concentration because of the likely evaporative processes occurring in those environments. Halophiles are UV resistant [3] and have an ability to entomb themselves within salt crystals during periods of desiccation [4], halophiles have therefore been proposed as analogues for potential martian life. Boulby Salt and Potash Mine in Yorkshire has excavations up to 1.4 km underground and is the second deepest mine in Europe. Despite this depth and the darkness, Norton et al., [5] isolated halophiles from the halite deposits. In this project, we will attempt to isolate and characterize halophiles from halite and other salt-rich sediments from Boulby Mine such as potash, sylvinite, anhydrite and polyhalite, in order to gain an understanding of potential life in the subsurface of Mars. Although the Boulby Mine is used as a martian analogue environment [6], it does possess certain key differences from modern Mars, in particular its aerobic environment and warm temperature. Our long-term goals, once we have characterized the micro-organisms present, are to expose them to Mars conditions (past and present) to determine their ability to grow in such environments. Elements of the martian environment being considered include variations in temperature, lack of oxygen and variations in brine composition. , We will then focus on defining molecular biomarkers and geochemical bio-signatures that may be used as evidence of past or present life on Mars. [1] [1] Mahaffy, P., et al., Science, 2014. [2] Sawyer, D.J., et al., Meteoritics & Planetary Science, 2000. 35(4): p. 743-747 [2] Fischer, E., et al. (2014). Geophysical Research Letters 41(13) [3] Landis, G.A., Astrobiology, 2001. 1(2): p. 161-4 [4] Grant, W. D., R. T. Gemmell and T. J. McGenity (1998). Halophiles. Extremophiles: Microbial Life in Extreme Envi

Our study is motivated by two aspects: i) the scientific motivation is to a) expand on previous studies of heavy noble gases in samples from terrestrial hot and cold deserts, thus to collect surface and subsurface (20 cm depth) samples from wind-blown desert soil and to b) study clay rich soil horizons for their microbiology and potential to serve as Mars analogue; and the ii) technological motivation is to field-test a prototype sampling container for crew-based sample return missions to Mars, the Moon, or other celestial bodies.

Raman spectroscopy is a powerful technique for the characterisation of organic molecules as it provides a unique ‘fingerprint’ spectrum. Incident monochromatic light on a sample is shifted in wavelength giving rise to the Raman spectrum, with peaks that are attributable to the specific vibrational bonds within the molecule. Raman spectroscopy is useful for analysing not only geological samples but also biological molecules, and has been recommended for use as a detection method (among others) for biomarkers on missions to planetary bodies [1]. The ExoMars Rover mission is due to launch in 2018 with a Raman spectrometer as part of its scientific payload [2]. Amino acids, the ‘building-blocks’ of proteins, have been identified as a high priority biomarker in the search for evidence of life on planetary bodies [3]. Raman spectroscopy is often a qualitative method, but if signatures of biomarkers are detected by Raman spectroscopy, it is critical that correct identification of such biomarkers can be undertaken. To aid in molecule identification, we take a statistical approach to determine the position of characteristic peaks of several amino acids. We present evidence for statistically significant changes in the peak positions when using different excitation wavelengths. Furthermore, we present evidence that martian conditions have an effect on the Raman spectra of amino acids, which could have implications when performing in situ measurements on Mars. 1. Jehlicka, J., H.G.M. Edwards, and P. Vítek, Assessment of Raman spectroscopy as a tool for the non-destructive identification of organic minerals and biomolecules for Mars studies. Planetary and Space Science, 2009. 57(5-6): p. 606-613. 2. Edwards, H.G.M., I. Hutchinson, and R. Ingley, The ExoMars Raman spectrometer and the identification of biogeological spectroscopic signatures using a flight-like prototype. Analytical and Bioanalytical Chemistry, 2012. 404(6-7

We report on new analogue materials to simulate Martian rocks and soils, especially under realistic redox conditions.

We have reviewed the current physical and chemical conditions of the Enceladus sub-surface environment, including the composition, temperature, pH and pressure. Here we have defined some of these parameters and, through the aid of modelling, will define and refine the remaining parameters needed for our experimental work. Simulations of the chemical reactions occurring within Enceladus can then be carried out to advance our understanding of the internal environment of Enceladus and help evaluate its potential habitability. Once a better understanding of the chemical reactions occurring at the rock-water interface has been carried out, then potential analogues on Earth can be evaluated and known microbial life can be tested to see if it could survive the conditions of Enceladus.

In the search for life elsewhere in the Solar System, our nearest planetary neighbour, Mars, offers great potential for finding past or present life. Whether life is extant or not, signs of biological activity can be inferred through the detection of specific biomarkers, such as amino acids. Raman spectroscopy is an extremely effective method of detecting biomarkers. It is non-destructive and is used to identify different molecular species through observations of the Raman shift created by the bonds within the molecule. Amino acids that are part of a biological system could provide potential evidence of life on Mars. It is thought that amino acids could survive in the sub-surface of Mars, making them a high-priority biomarker candidate. Terrestrial life utilises homochiral amino acids, and if detected on Mars it would provide an important piece of evidence for the case for life on Mars. In this work, a number of biologically essential amino acids that are utilised in terrestrial organisms will be studied using Raman spectroscopy. We aim to characterise the Raman signature for these molecules in detail in order to aid interpretation of results from future Mars landers, and presented here are initial results from the preliminary investigations. Further work will extend to other high-priority biomarkers that may be found at the surface/sub-surface of Mars.

The first step in finding potential extant, and/or extinct, life on Mars is to understand the potential biological processes that may have occurred on Mars. This is dependent on identifying and characterising microbial life in suitable terrestrial analogue environments. Chemolithotrophic anaerobic microorganisms, such as methanogens, are ideal organisms for investigating potential life on Mars. In this study, we used a community of chemolithotrophic anaerobic microorganisms, which were isolated from below the redox potential discontinuity (RPD) layer of the River Dee estuary, UK. The anaerobic conditions, the 11-15˚C temperature and high salinity make the sub-RPD zone an ideal analogue for the Martian subsurface. Using 454 sequencing we investigated the composition of the microbial community which included sulfate reducing bacteria. Anaerobic growth experiments were conducted with a basalt and aegirine growth medium, which were used as an analogue for the composition of the Rocknest site on Mars. The microbial community was able to grow, utilising the bio-essential elements in the growth medium. The dissolution kinetics were determined by measuring the release of key elements, such as Si, Ca, K, Fe in the growth medium with ICP-AES and growth was measured by cell counts The results from this study demonstrate that the microbial community below the RPD can act as an informative analogue in studies of Martian habitability and life detection.