Recent and proposed robotic missions to Mars are equipped with implements to expose or excavate fresh material from beneath the immediate surface. Once brought into the open, any organic molecules or potential biosignatures of present or past life will be exposed to the unfiltered solar ultraviolet (UV) radiation and face photolytic degradation over short time courses. The key question, then, is what is the window of opportunity for detection of recently exposed samples during robotic operations? Detection of autofluorescence has been proposed as a simple method for surveying or triaging samples for organic molecules. Using a Mars simulation chamber we conduct UV exposures on thin frozen layers of two model microorganisms, the radiation-resistant polyextremophile Deinococcus radiodurans and the cyanobacterium Synechocystis sp. PCC 6803. Excitation–emission matrices (EEMs) are generated of the full fluorescence response to quantify the change in signal of different cellular fluorophores over Martian equivalent time. Fluorescence of Deinococcus cells, protected by a high concentration of carotenoid pigments, was found to be relatively stable over 32 h of Martian UV irradiation, with around 90% of the initial signal remaining. By comparison, fluorescence from protein-bound tryptophan in Synechocystis is much more sensitive to UV photodegradation, declining to 50% after 64 h exposure. The signal most readily degraded by UV irradiation is fluorescence of the photosynthetic pigments – diminished to only 35% after 64 h. This sensitivity may be expected as the biological function of chlorophyll and phycocyanin is to optimize the harvesting of light energy and so they are readily photobleached. A significant increase in a ∼450 nm emission feature is interpreted as accumulation of fluorescent cellular degradation products from photolysis. Accounting for diurnal variation in Martian sunlight, this study calculates that frozen cellular biosignatures would remain detectable by fluorescence for at least several sols; offering a sufficient window for robotic exploration operations.

We address the possibility that intelligent civilizations that destroy themselves could present signatures observable by humanity. Placing limits on the number of self-destroyed civilizations in the Milky Way has strong implications for the final three terms in Drake's Equation, and would allow us to identify which classes of solution to Fermi's Paradox fit with the evidence (or lack thereof). Using the Earth as an example, we consider a variety of scenarios in which humans could extinguish their own technological civilization. Each scenario presents some form of observable signature that could be probed by astronomical campaigns to detect and characterize extrasolar planetary systems. Some observables are unlikely to be detected at interstellar distances, but some scenarios are likely to produce significant changes in atmospheric composition that could be detected serendipitously with next-generation telescopes. In some cases, the timing of the observation would prove crucial to detection, as the decay of signatures is rapid compared with humanity's communication lifetime. In others, the signatures persist on far longer timescales.

Future space missions that aim to detect life should search for molecules that are vital to all living organisms. Although the Viking landers did not find any signs of organic molecules on Mars, signatures of past and/or present life may still exist in the Martian regolith. In this paper, we describe amino acid analyses performed in several Martian analogue soil samples collected close to the Mars Desert Research Station (MDRS), Utah, during the International Lunar Exploration Working Group (ILEWG) EuroGeoMars campaign in February 2009. The Utah desert around Hanksville is characterized as shale desert and is cold and arid with an average annual temperature of 12°C. It is subjected to wind erosion and was shaped by fluvial erosion. The data show large differences in the total amino acid abundances between all the collected soil samples, with values ranging from non-detectable to 100 000 parts per billion (ppb). These results are explained in the context of mineralogical differences (namely different clay content) among the soil samples. The data have implications for future life-detection missions and the target mineralogy that may host biological signatures.

Planets with masses between 0.1 and 10 M⊕ are believed to host dense atmospheres. These atmospheres can play an important role on the planet's spin evolution, since thermal atmospheric tides, driven by the host star, may counterbalance gravitational tides. In this work, we study the long-term spin evolution of Earth-sized exoplanets. We generalize previous works by including the effect of eccentric orbits and obliquity. We show that under the effect of tides and core–mantle friction, the obliquity of the planets evolves either to 0° or 180°. The rotation of these planets is also expected to evolve into a very restricted number of equilibrium configurations. In general, none of these equilibria is synchronous with the orbital mean motion. The role of thermal atmospheric tides becomes more important for Earth-sized planets in the habitable zones of their systems; so they cannot be neglected when we search for their potential habitability.

Evolution, broadly construed, has become a powerful unifying concept in much of science – not only in the biological evolution of plants and animals, but also in the physical evolution of stars and planets, and the cultural evolution of society and its many varied products. This paper (1) explores the bulk structure and functioning of open, non-equilibrium, thermodynamic systems relevant to the interdisciplinary field of astrobiology, (2) places the astrobiological landscape into an even larger, cosmological context, (3) defines life, complexity and evolution writ large, (4) claims that life depends ultimately on the expansion of the Universe and the flow of energy derived therefrom and (5) proposes a quantitative metric to characterize the rise of complexity throughout all of natural history. That metric is neither information nor negentropy, for these inveterate yet qualitative terms cannot be quantified, nor even defined, to everyone's satisfaction in today's scientific community. Rather, the newly proposed metric is normalized energy flow, a revision of a long-cherished term – energy – that is physically intuitive, well defined and readily measurable. All ordered systems – from rocky planets and shining stars, to buzzing bees and redwood trees – can be best judged empirically and uniformly by gauging the amount of energy acquired, stored and expressed by those systems. Appeals to anthropism are unnecessary to appreciate the impressive hierarchy of the cosmic evolutionary narrative, including a technological civilization that now embraces an energetics agenda designed to better understand, and perhaps to unify, all the natural sciences.

We describe the field demonstration of astrobiology instruments and research methods conducted in and from the Mars Desert Research Station (MDRS) in Utah during the EuroGeoMars campaign 2009 coordinated by ILEWG, ESA/ESTEC and NASA Ames, with the contribution of academic partners. We discuss the entire experimental approach from determining the geological context using remote sensing, in situ measurements, sorties with sample collection and characterization, analysis in the field laboratory, to the post sample analysis using advanced laboratory facilities.

We present the rationale for terrestrial field campaigns to strengthen astrobiology research and the link between in situ and orbital remote sensing data. These campaigns are supporting the preparation for future missions such as Mars Science Laboratory, ExoMars or Mars Sample Return. We describe the EuroGeoMars 2009 campaign conducted by MDRS crew 76 and 77, focused on the investigation of surface processes in their geological context. Special emphasis was placed on sample collection and pre-screening using in-situ portable instruments. Science investigations included geological and geochemical measurements as well as detection and diagnostic of water, oxidants, organic matter, minerals, volatiles and biota.

EuroGeoMars 2009 was an example of a Moon–Mars field research campaign dedicated to the demonstration of astrobiology instruments and a specific methodology of comprehensive measurements from selected sampling sites. We discuss in sequence: the campaign objectives and trade-off based on science, technical or operational constraints. This includes remote sensing data and maps, and geological context; the monitoring of environmental parameters; the geophysical context and mineralogy studies; geology and geomorphology investigations; geochemistry characterization and subsurface studies.

We describe sample handling (extraction and collection) methods, and the sample analysis of soils and rocks performed in the MDRS laboratory using close inspection, initial petrological characterization, microscopy, Visible-NIR spectrometry, Raman spectrometry, X-ray diffraction/X-ray fluorescence spectrometry, soil analysis, electrochemical and biological measurements.

The results from post-mission analysis of returned samples using advanced facilities in collaborator institutes are described in companion papers in this issue. We present examples of in-situ analysis, and describe an example investigation on the exploration and analysis of endolithic microbial mats (from reconnaissance, in-situ imaging, sampling, local analysis to post-mission sample analysis).

We examined the environmental stresses experienced by cyanobacteria living in endolithic gneissic habitats in the Haughton impact structure, Devon Island, Canadian High Arctic (75° N) and compared them with the endolithic habitat at the opposite latitude in the Dry Valleys of Antarctica (76° S). In the Arctic during the summer, there is a period for growth of approximately 2.5 months when temperatures rise above freezing. During this period, freeze–thaw can occur during the diurnal cycle, but freeze–thaw excursions are rare within higher-frequency temperature changes on the scale of minutes, in contrast with the Antarctic Dry Valleys. In the Arctic location rainfall of approximately 3 mm can occur in a single day and provides moisture for endolithic organisms for several days afterwards. This rainfall is an order of magnitude higher than that received in the Dry Valleys over 1 year. In the Dry Valleys, endolithic communities may potentially receive higher levels of ultraviolet radiation than the Arctic location because ozone depletion is more extreme. The less extreme environmental stresses experienced in the Arctic are confirmed by the presence of substantial epilithic growth, in contrast to the Dry Valleys. Despite the more extreme conditions experienced in the Antarctic location, the diversity of organisms within the endolithic habitat, which includes lichen and eukaryotic algal components, is higher than observed at the Arctic location, where genera of cyanobacteria dominate. The lower biodiversity in the Arctic may reflect the higher water flow through the rocks caused by precipitation and the more heterogeneous physical structure of the substrate. The data illustrate an instance in which extreme climate is anti-correlated with microbial biological diversity.

If life occurs elsewhere in the Solar System, there is a strong likelihood that it occurs in a deep biosphere beneath the planetary surface. The evidence for methane in the martian atmosphere has drawn attention to the possible role of serpentinites in fuelling a deep biosphere through the generation of hydrogen and/or methane. Serpentinites represent a good target for the search for biosignatures in a range of reaction products. Isotopic measurements in each of methane, sulphide and carbonate in serpentinites can help determine evidence of biological activity. We show that ancient terrestrial serpentinites retain methane that could be subject to the measurement of carbon and hydrogen isotopes. There is, therefore, potential to sample serpentinites on Mars and test for evidence of life in the deep geological record of Mars.

In order to confirm the results of previous experiments concerning the chemical behaviour of organic molecules in the space environment, organic molecules (amino acids and a dipeptide) in pure form and embedded in meteorite powder were exposed in the AMINO experiment in the EXPOSE-R facility onboard the International Space Station. After exposure to space conditions for 24 months (2843 h of irradiation), the samples were returned to the Earth and analysed in the laboratory for reactions caused by solar ultraviolet (UV) and other electromagnetic radiation. Laboratory UV exposure was carried out in parallel in the Cologne DLR Center (Deutsches Zentrum für Luft und Raumfahrt). The molecules were extracted from the sample holder and then (1) derivatized by silylation and analysed by gas chromatography coupled to a mass spectrometer (GC–MS) in order to quantify the rate of degradation of the compounds and (2) analysed by high-resolution mass spectrometry (HRMS) in order to understand the chemical reactions that occurred. The GC–MS results confirm that resistance to irradiation is a function of the chemical nature of the exposed molecules and of the wavelengths of the UV light. They also confirm the protective effect of a coating of meteorite powder. The most altered compounds were the dipeptides and aspartic acid while the most robust were compounds with a hydrocarbon chain. The MS analyses document the products of reactions, such as decarboxylation and decarbonylation of aspartic acid, taking place after UV exposure. Given the universality of chemistry in space, our results have a broader implication for the fate of organic molecules that seeded the planets as soon as they became habitable as well as for the effects of UV radiation on exposed molecules at the surface of Mars, for example.

Chemical and microbiological studies of the impact of terrestrial contamination of the lunar surface during the Apollo missions could provide valuable data to help refine future Mars surface exploration plans and planetary protection requirements for a human mission to Mars. NASA and ESA have outlined new visions for solar system exploration that will include a series of lunar robotic missions to prepare for and support a human return to the Moon, and future human exploration of Mars and other destinations. Under the Committee on Space Research's (COSPAR's) current planetary protection policy for the Moon, no decontamination procedures are required for outbound lunar spacecraft. Nonetheless, future in situ investigations of a variety of locations on the Moon by highly sensitive instruments designed to search for biologically derived organic compounds would help assess the contamination of the Moon by lunar spacecraft and Apollo astronauts. These studies could also provide valuable ‘ground truth’ data for Mars sample return missions and help define planetary protection requirements for future Mars bound spacecraft carrying life detection experiments.

In this paper, in this edition of the Journal commemorating the life and work of David Wynn-Williams, we consider approaches to the astrobiological investigation of Mars. We provide a brief account of the scientific rationale behind the approach presented here. In particular, we outline the capabilities of the Raman spectrometer for the detection of biomarkers. David Wynn-Williams was an active champion of this instrument who was keen to field-qualify a version in Antarctica with a view to flying a Raman instrument onboard a Mars-bound space mission. We examine a scenario for the deployment of such an instrument in conjunction with other instrumentation and argue that subsurface deployment of scientific instruments is essential if we are to succeed in detecting any evidence that may exist for former life on Mars. We outline a mission scenario – Vanguard – which represents a novel but low-risk, low-cost approach to Mars exploration that was conceived and developed jointly by one of the authors (Ellery) and the late David Wynn-Williams.

The adsorption of organic molecules on mineral matrices might have played a fundamental role in processes that led to the emergence of life. We investigated the adsorption properties of the nucleobases adenine, cytosine, uracil and hypoxanthine on magnesium oxide (MgO), determining the single solute batch equilibrium adsorption isotherms. Langmuir-type isotherms were fitted to data, assuming a rapid reversible equilibration of adsorption, demonstrated effectively through desorption experiments. The Langmuir equilibrium adsorption constant K and the amount of the solute per unit of adsorbent mass necessary to complete the monolayer b were calculated. The results indicate that MgO is a good adsorbent for nucleobases (adenine > uracil > hypoxantine > cytosine), suggesting a role of metal oxides in concentrating biomolecules in prebiotic conditions that might have favoured the passage from geochemistry to biochemistry.

Hot Lake (Oroville, WA) is an athalassohaline epsomite lake that can have precipitating concentrations of MgSO4 salts, mainly epsomite. Little biotic study has been done on epsomite lakes and it was unclear whether microbes isolated from epsomite lakes and their margins would fall within recognized halotolerant genera, common soil genera or novel phyla. Our initial study cultivated and characterized epsotolerant bacteria from the lake and its margins. Approximately 100 aerobic heterotrophic microbial isolates were obtained by repetitive streak-plating in high-salt media including either 10% NaCl or 2 M MgSO4. The collected isolates were all bacteria, nearly evenly divided between Gram-positive and Gram-negative clades, the most abundant genera being Halomonas, Idiomarina, Marinobacter, Marinococcus, Nesterenkonia, Nocardiopsis and Planococcus. Bacillus, Corynebacterium, Exiguobacterium, Kocuria and Staphylococcus also were cultured. This initial study included culture-independent community analysis of direct DNA extracts of lake margin soil using PCR-based clone libraries and 16S rRNA gene phylogeny. Clones assigned to Gram-positive bacterial clades (70% of total clones) were dominated by sequences related to uncultured actinobacteria. There were abundant Deltaproteobacteria clones related to bacterial sulphur metabolisms and clones of Legionella and Coxiella. These epsomite lake microbial communities seem to be divided between bacteria primarily associated with hyperhaline environments rich in NaCl and salinotolerant relatives of common soil organisms. Archaea appear to be in low abundance and none were isolated, despite near-saturated salinities. Growth of microbes at very high concentrations of magnesium and other sulphates has relevance to planetary protection and life-detection missions to Mars, where scant liquid water may form as deliquescent brines and appear as eutectic liquids.

Interstellar probes can carry out slingshot manoeuvres around the stars they visit, gaining a boost in velocity by extracting energy from the star's motion around the Galactic Centre. These manoeuvres carry little to no extra energy cost, and in previous work it has been shown that a single Voyager-like probe exploring the Galaxy does so 100 times faster when carrying out these slingshots than when navigating purely by powered flight (Forgan et al. 2012). We expand on these results by repeating the experiment with self-replicating probes. The probes explore a box of stars representative of the local Solar neighbourhood, to investigate how self-replication affects exploration timescales when compared with a single non-replicating probe. We explore three different scenarios of probe behaviour: (i) standard powered flight to the nearest unvisited star (no slingshot techniques used), (ii) flight to the nearest unvisited star using slingshot techniques and (iii) flight to the next unvisited star that will give the maximum velocity boost under a slingshot trajectory. In all three scenarios, we find that as expected, using self-replicating probes greatly reduces the exploration time, by up to three orders of magnitude for scenarios (i) and (iii) and two orders of magnitude for (ii). The second case (i.e. nearest-star slingshots) remains the most time effective way to explore a population of stars. As the decision-making algorithms for the fleet are simple, unanticipated ‘race conditions’ among probes are set up, causing the exploration time of the final stars to become much longer than necessary. From the scaling of the probes' performance with star number, we conclude that a fleet of self-replicating probes can indeed explore the Galaxy in a sufficiently short time to warrant the existence of the Fermi Paradox.

The concept of sustainability is widely acknowledged as a political guideline. Economic, ecological, social and cultural aspects of sustainability are already under discussion. Current space mining efforts demand that the discussion become a broader one about ‘planetary sustainability’, including the space surrounding Earth. To date, planetary sustainability has mainly been used with reference to Earth only and I will extend it here, elaborating on a similar NASA initiative. This article (1) sketches the contemporary economic–political initiatives which call for a special reflection of Earth's location in space, and then (2) discusses the meaning of the concept of sustainability in this context. Next, (3) I relate the discussion to the issue of planetary and environmental protection, before, (4) finally, presenting a philosophical and theological perspective that seems particularly able to broach the issue of the multiple dimensions of sustainability in this context. This is the concept of constructive-critical realism. My overview of the topic concludes with (5) a summarizing outlook.

I propose a unified framework for a joint analysis of the Drake equation and the Fermi paradox, which enables a simultaneous, quantitative study of both of them. The analysis is based on a simplified form of the Drake equation and on a fairly simple scheme for the colonization of the Milky Way. It appears that for sufficiently long-lived civilizations, colonization of the Galaxy is the only reasonable option to gain knowledge about other life forms. This argument allows one to define a region in the parameter space of the Drake equation, where the Fermi paradox definitely holds (‘Strong Fermi paradox’).

Tests on cyanobacteria communities embedded in cryptobiotic crusts collected in hot and cold deserts on Earth were performed under Mars-like conditions. The simulations were realized as a survey, to find the best samples for future research. During the tests organisms have to resist Mars-like conditions such as atmospheric composition, pressure, variable humidity (saturated and dry conditions) and partly strong UV irradiation. Organisms were tested within their original habitat inside the crust. Nearly half of the cryptobiotic samples from various sites showed survival of a substantial part of their coexisting organisms. The survival in general depended more on the nature of the original habitat and type of the sample than on the different conditions they were exposed to. The best survival was observed in samples from United Arab Emirates (Jebel Ali, 25 km SW of Dubai town) and from Western Australia (near the South edge of Lake Barley), by taxa: Tolypothrix byssoidea, Gloeocapsopsis pleurocapsoides, Nostoc microscopicum, Leptolyngbya or Symploca sp. At both places in salty desert areas members of the Chenopodiaceae family dominated among the higher plants and in the cryptobiotic crust cyanobacterial taxa Tolypothrix was dominant. These organisms were all living in salty locations with dry conditions most of the year. Among them Tolypothrix, Gloeocapsopsis and Symploca sp. were tested in Mars simulation chambers for the first time. The results suggest that extremophiles should be tested with taken into account the context of their original microenvironment, and also the importance to analyse communities of microbes beside single organisms.

Cosmic rays may be linked to the formation of volatiles necessary for prebiotic chemistry. We explore the effect of cosmic rays in a hydrogen-dominated atmosphere, as a proof-of-concept that ion–neutral chemistry may be important for modelling hydrogen-dominated atmospheres. In order to accomplish this, we utilize Monte Carlo cosmic ray transport models with particle energies of 106 eV<E<1012 eV in order to investigate the cosmic-ray enhancement of free electrons in substellar atmospheres. Ion–neutral chemistry is then applied to a Drift–Phoenix model of a free-floating giant gas planet. Our results suggest that the activation of ion–neutral chemistry in the upper atmosphere significantly enhances formation rates for various species, and we find that C2H2, C2H4, NH3, C6H6 and possibly C10H are enhanced in the upper atmospheres because of cosmic rays. Our results suggest a potential connection between cosmic-ray chemistry and the hazes observed in the upper atmospheres of various extrasolar planets. Chemi-ionization reactions are briefly discussed, as they may enhance the degree of ionization in the cloud layer.

In the context of astrobiological exposure and simulation experiments in the BIOMEX project, the lichen Circinaria gyrosa was investigated by Raman microspectroscopy. Owing to the symbiotic nature of lichens and their remarkable extremotolerance, C. gyrosa represents a valid model organism in recent and current astrobiological research. Biogenic compounds of C. gyrosa were studied that may serve as biomarkers in Raman assisted remote sensing missions, e.g. ExoMars. The surface as well as different internal layers of C. gyrosa have been characterized and data on the detectability and distribution of β-carotene, chitin and calcium oxalate monohydrate (whewellite) are presented in this study. Raman microspectroscopy was applied on natural samples and thin sections. Although calcium oxalates can also be formed by rare geological processes it may serve as a suitable biomarker for astrobiological investigations. In the model organism C. gyrosa, it forms extracellular crystalline deposits embedded in the intra-medullary space and its function is assumed to balance water uptake and gas exchange during the rare, moist to wet environmental periods that are physiologically favourable. This is a factor that was repeatedly demonstrated to be essential for extremotolerant lichens and other organisms. Depending on the decomposition processes of whewellite under extraterrestrial environmental conditions, it may not only serve as a biomarker of recent life, but also of past and fossilized organisms.

In this paper we present a unified, quantitative synthesis of analytical and numerical calculations of the effects that could be caused on Earth by a gamma-ray burst (GRB), considering atmospheric and biological implications. The main consequences of the illumination by a GRB are grouped into four distinct classes and analysed separately, namely: direct γ flash, UV flash, O3 layer depletion and cosmic rays. The effectiveness of each of these classes is compared and distances for significant biological damage are given for each one. We find that the first three effects have the potential to cause global environmental changes and biospheric damage, even if the source is located at galactic distances or even farther afield (up to 150 kpc, where 1 parsec=3.09×1016 m, about five times the Galactic diameter of 30 kpc). Instead, cosmic rays would only be a serious threat for close sources (of the order of a few parsecs).

As a concrete application from a well-recorded event, the effects on the biosphere of an event identical to the giant flare of SGR1806-20 on 27 December 2004 have been calculated. In spite of not belonging to the so-called ‘classical’ GRBs, most of the parameters of this recent flare are quite well known and have been used as a calibration for our study. We find that a giant flare impinging on Earth is not a threat for life in all practical situations, mainly because it is not as energetic, in spite of being much more frequent than GRBs, unless the source happens to be extremely close.