Low atmospheric pressures on Mars and the lack of substantial amounts of liquid water were suggested to be among the major limiting factors for the potential Martian biosphere. However, large amounts of ice were detected in the relatively shallow subsurface layers of Mars by the Odyssey Mission and when ice sublimates the water vapour can diffuse through the porous surface layer of the soil. Here we studied the possibility for the active growth of microorganisms in such a vapour diffusion layer. Our results showed the possibility of metabolism and the reproduction of non-extremophile terrestrial microorganisms (Vibrio sp.) under very low (0.01–0.1 mbar) atmospheric pressures in a Martian-like shallow subsurface regolith.

This paper highlights unique sites in Ladakh, India, investigated during our 2016 multidisciplinary pathfinding expedition to the region. We summarize our scientific findings and the site's potential to support science exploration, testing of new technologies and science protocols within the framework of astrobiology research. Ladakh has several accessible, diverse, pristine and extreme environments at very high altitudes (3000–5700 m above sea level). These sites include glacial passes, sand dunes, hot springs and saline lake shorelines with periglacial features. We report geological observations and environmental characteristics (of astrobiological significance) along with the development of regolith-landform maps for cold high passes. The effects of the diurnal water cycle on salt deliquescence were studied using the ExoMars Mission instrument mockup: HabitAbility: Brines, Irradiance and Temperature (HABIT). It recorded the existence of an interaction between the diurnal water cycle in the atmosphere and salts in the soil (which can serve as habitable liquid water reservoirs). Life detection assays were also tested to establish the best protocols for biomass measurements in brines, periglacial ice-mud and permafrost melt water environments in the Tso-Kar region. This campaign helped confirm the relevance of clays and brines as interest targets of research on Mars for biomarker preservation and life detection.

One of the primary open questions of astrobiology is whether there is extant or extinct life elsewhere the solar system. Implicit in much of this work is that we are looking for microbial or, at best, unintelligent life, even though technological artefacts might be much easier to find. Search for Extraterrestrial Intelligence (SETI) work on searches for alien artefacts in the solar system typically presumes that such artefacts would be of extrasolar origin, even though life is known to have existed in the solar system, on Earth, for eons. But if a prior technological, perhaps spacefaring, species ever arose in the solar system, it might have produced artefacts or other technosignatures that have survived to present day, meaning solar system artefact SETI provides a potential path to resolving astrobiology's question. Here, I discuss the origins and possible locations for technosignatures of such a prior indigenous technological species, which might have arisen on ancient Earth or another body, such as a pre-greenhouse Venus or a wet Mars. In the case of Venus, the arrival of its global greenhouse and potential resurfacing might have erased all evidence of its existence on the Venusian surface. In the case of Earth, erosion and, ultimately, plate tectonics may have erased most such evidence if the species lived Gyr ago. Remaining indigenous technosignatures might be expected to be extremely old, limiting the places they might still be found to beneath the surfaces of Mars and the Moon, or in the outer solar system.

The ‘holy grail’ in planet hunting is the detection of an Earth-analogue: a planet with similar mass as the Earth and an orbit inside the habitable zone. If we can find such an Earth-analogue around one of the stars in the immediate solar neighbourhood, we could potentially even study it in such great detail to address the question of its potential habitability. Several groups have focused their planet detection efforts on the nearest stars. Our team is currently performing an intensive observing campaign on the α Centauri system using the High Efficiency and Resolution Canterbury University Large Échelle Spectrograph (Hercules) at the 1 m McLellan telescope at Mt John University Observatory in New Zealand. The goal of our project is to obtain such a large number of radial velocity (RV) measurements with sufficiently high temporal sampling to become sensitive to signals of Earth-mass planets in the habitable zones of the two stars in this binary system. Over the past few years, we have collected more than 45 000 spectra for both stars combined. These data are currently processed by an advanced version of our RV reduction pipeline, which eliminates the effect of spectral cross-contamination. Here we present simulations of the expected detection sensitivity to low-mass planets in the habitable zone by the Hercules programme for various noise levels. We also discuss our expected sensitivity to the purported Earth-mass planet in a 3.24-day orbit announced by Dumusque et al. (2012).

Episodes of species mass extinction dramatically affected the evolution of life on Earth, but their causes remain a source of debate. Even more controversy surrounds the hypothesis of periodicity in the fossil record, with conflicting views still being published in the scientific literature, often even based on the same state-of-the-art datasets. From an empirical point of view, limitations of the currently available data on extinctions and possible causes remain an important issue. From a theoretical point of view, it is likely that a focus on single extinction causes and strong periodic forcings has strongly contributed to this controversy. Here I show that if there is a periodic extinction signal at all, it is much more likely to result from a combination of a comparatively weak periodic cause and various random factors. Tests of this unified model of mass extinctions on the available data show that the model is formally better than a model with random extinction causes only. However, the contribution of the periodic component is small compared to factors such as impacts or volcanic eruptions.

A simulation experiment with a complex bacterial soil community in a Mars simulation chamber was performed to determine the effect of Martian conditions on community activity, stability and survival. At three different depths in the soil core short-term effects of Martian conditions with and without ultraviolet (UV) exposure corresponding to 8 Martian Sol were compared. Community metabolic activities and functional diversity, measured as glucose respiration and versatility in substrate utilization, respectively, decreased after UV exposure, whereas they remained unaffected by Martian conditions without UV exposure. In contrast, the numbers of culturable bacteria and the genetic diversity were unaffected by the simulated Martian conditions both with and without UV exposure. The genetic diversity of the soil community and of the colonies grown on agar plates were evaluated by denaturant gradient gel electrophoresis (DGGE) on DNA extracts. Desiccation of the soil prior to experimentation affected the functional diversity by decreasing the versatility in substrate utilization. The natural dominance of endospores and Gram-positive bacteria in the investigated Mars-analogue soil may explain the limited effect of the Mars incubations on the survival and community structure. Our results suggest that UV radiation and desiccation are major selecting factors on bacterial functional diversity in terrestrial bacterial communities incubated under simulated Martian conditions. Furthermore, these results suggest that forward contamination of Mars is a matter of great concern in future space missions.

Techniques enabling in situ elemental and mineralogical analysis on extraterrestrial planets are strongly required for upcoming missions and are being continuously developed. There is ample need for quantitative and high-sensitivity analysis of elemental as well as isotopic composition of heterogeneous materials. Here we present in situ spatial and depth elemental profiles of a heterogeneous rock sample on a depth-scale of nanometres using a miniaturized laser ablation mass spectrometer (LMS) designed for planetary space missions. We show that the LMS spectra alone could provide highly detailed compositional, three-dimensional information and oxidation properties of a natural, heterogeneous rock sample. We also show that a combination of the LMS and Raman spectroscopy provide comprehensive mineralogical details of the investigated sample. These findings are of great importance for future space missions where quick, in situ determination of the mineralogy could play a role in the process of selecting a suitable spot for drilling.

We studied the effects of soft X-rays radiation on free and clay (montmorillonite, kaolinite) adsorbed DNA. The DNA samples were exposed to X-rays of 1.49, 4.51 and 8.04 keV for exposure times ranging from 2 min up to 16 h. The biological transformation technique was used to estimate the damage of the DNA molecules. Free and clay adsorbed DNA are differently affected by X-rays. The former is damaged by X-rays and the level of damage depends on the energy dose rather than the hardness of the radiation. The clay adsorbed DNA is not damaged by X-rays for energy doses up to 5.8×104 erg. Clays materials could have protected the building blocks of life on the primordial Earth when the solar X-ray emission was much stronger than today.

The aim of the paper is to present the time profile of cosmic radiation exposure obtained by the radiation risks radiometer-dosimeter (R3DR) during the ESA exposition facility for EXPOSE-R mission (EXPOSE-R) in the EXPOSE-R facility outside the Russian Zvezda module of the International Space Station (ISS). Another aim is to make the obtained results available to other EXPOSE-R teams for use in their data analysis. R3DR is a low mass and small dimensions automated device, which measures solar radiation in four channels and in addition cosmic ionizing radiation. The main results of cosmic ionizing radiation measurements are: three different radiation sources were detected and quantified: galactic cosmic rays (GCR), energetic protons from the inner radiation belt (IRB) in the region of the South Atlantic anomaly and energetic electrons from the outer radiation belt (ORB). The highest daily averaged absorbed dose rate of 506 μGy day−1 came from IRB protons; GCR delivered much smaller daily absorbed dose rates of 81.4 μGy day−1 on average, and ORB source delivered on average a dose rate of 89 μGy day−1. The IRB and ORB daily averaged absorbed dose rates were higher than those observed during the ESA exposition facility for EXPOSE-E mission (EXPOSE-E), whereas the GCR rate was smaller than that measured during the EXPOSE-E mission. The reason for this difference is much less surrounding constructions shielding of the R3DR instrument in comparison with the R3DE instrument.

Template-directed polymer assembly is a likely feature of prebiotic chemistry, but the product blocks further synthesis, preventing amplification and Darwinian selection. Nucleic acids are unusual because charge repulsion between opposing phosphates permits salt-dependent association and dissociation. It was postulated (Lathe, R. (2004). Fast tidal cycling and the origin of life. Icarus168, 18–22) that tides at ocean shores provide the driving force for amplification: evaporative concentration promoted association/assembly on drying, while charge repulsion on tidal dilution drove dissociation. This permits exponential amplification by a process termed here the tidal chain reaction (TCR). The process is not strictly contingent upon tidal ebb and flow: circadian dews and rainfalls can produce identical cycling. Ionic strength-dependent association and dissociation of nucleic acids and possible prebiotic precursors are reviewed. Polymer scavenging, chain assembly by the recruitment of pre-formed fragments, is proposed as the primary mechanism of reiterative chain assembly. Parameters determining prebiotic polymer structure and amplification by TCR are discussed, with the suggestion that Darwinian selection may have operated on families of related polymers rather than on individual molecules.

Subglacially erupted Neogene basaltic hyaloclastites in lava-fed deltas in Antarctica were found to contain putative endolithic microborings preserved in fresh glass along hydrous alteration boundaries. The location and existence over the past 6 Ma of these lava deltas has exposed them to successive interglacials and subsequent percolation of the hyaloclastite with marine water. A statistical study of the hyaloclastites has found that endolithic microborings are distinctly more abundant within samples that show evidence for marine alteration, compared with those that have remained in a strictly freshwater (glacial) environment. Additionally, correlation between elevation and the abundance of microborings shows endolithic activity to be more prolific within lower elevation samples, where the hyaloclastites were influenced by marine fluids. Our study strongly suggests that endolithic microborings form more readily in marine-influenced, rather than freshwater environments. Indeed, marine fluids may be a necessary precondition for the microbial activity responsible. Thus, we suggest that the chemistry and origin of alteration fluids are controlling factors on the formation of endolithic microborings in basaltic glass. The study also contributes to the understanding of how endolithic microborings could be used as a biosignature on Mars, where basaltic lavas and aqueous alteration are known to have existed in the past.

Recently reported results from latest Mars Orbiters and Rovers missions are transforming our opinion about the red planet. That dry and inhospitable planet reported in the past is becoming a wetter planet with high probabilities of water existence in the past. Nowadays, some results seem to indicate the presence of water beneath the Mars surface. But also mineralogy studies by NASA Opportunity Rover report iron oxides and hydroxides precipitates on Endurance Crater. Sedimentary deposits have been identified at Meridiani Planum. These deposits must have generated in a dune aqueous acidic and oxidizing environment. Similarities appear when we study Rio Tinto, and acidic river under the control of iron.

The discovery of extremophiles on Earth widened the window of possibilities for life to develop in the Universe, and as a consequence on Mars and other planetary bodies with astrobiological interest. The compilation of data produced by the ongoing missions offers an interested view for life possibilities to exist: signs of an early wet Mars and rather recent volcanic activity as well as ground morphological characteristics that seem to be promoted by liquid water. The discovery of important accumulations of sulfates and the existence of iron minerals such as jarosite in rocks of sedimentary origin has allowed specific terrestrial models to come into focus. Río Tinto (Southwestern Spain, Iberian Pyritic Belt) is an extreme acidic environment, product of the chemolithotrophic activity of micro-organisms that thrive in the massive pyrite-rich deposits of the Iberian Pyritic Belt. Some particular protective environments should house the organic molecules and bacterial life forms in harsh environments such as Mars surface supporting microniches inside precipitated minerals or inside rocks. Terrestrial analogues could help us to afford the comprehension of habitability (on other planetary bodies).

We are reporting here the multidisciplinary study of some endolithic niches inside salt deposits used by phototrophs for taking advantage of sheltering particular light wavelengths. These acidic salts deposits located in Río Tinto shelter life forms that are difficult to visualize by eye. This interdisciplinary field analogue campaign was conducted in the framework of the CAREX FP7 EC programme.

Carbonate minerals such as dolomite, kutnahorite or rhodochrosite are frequently, but not exclusively generated by microbial processes. In recent anoxic sediments, Mn(II)carbonate minerals (e.g. rhodochrosite, kutnahorite) derive mainly from the reduction of Mn(IV) compounds by anaerobic respiration. The formation of huge manganese-rich (carbonate) deposits requires effective manganese redox cycling in an oxygenated atmosphere. However, putative anaerobic pathways such as microbial nitrate-dependent manganese oxidation, anoxygenic photosynthesis and oxidation in ultraviolet light may facilitate manganese cycling even in an early Archean environment, without the availability of oxygen. In addition, manganese carbonates precipitate by microbially induced processes without change of the oxidation state, e.g. by pH shift. Hence, there are several ways how these minerals could have been formed biogenically and deposited in Precambrian sediments. We will summarize microbially induced manganese carbonate deposition in the presence and absence of atmospheric oxygen and we will make some considerations about the biogenic deposition of manganese carbonates in early Archean settings.

The extensive evidence of an ocean over a silicate nucleus makes Europa a candidate for the emergence of a second evolutionary pathway of autochthonous life. We argue that the most urgent question in astrobiology is the origin of habitable ecosystems (a question in geochemistry), rather than the alternative search for the origin of life itself (a question in chemical evolution). Since certain Solar System bodies may share a similar geophysical past with Earth, our more modest approach forces upon us the question: Can available instrumentation be the ‘pioneer’ in the discovery of habitable ecosystems in geophysical environments similar to the early Earth? It will be shown that a central piece in this dilemma is the chemical element sulphur (S). The Europan non-ice surficial elements that distort the water–ice absorption bands were found to be widespread, patchy and, most likely, endogenous. The Galileo Mission discovered these patches, which were subsequently confirmed by the 2007 flyby of New Horizons. We argue that penetrators should be inserted into orbital probes in the future exploration of Jupiter's System. Penetrators provide what could be a key instrument in the exploration of Europa, given the adverse space weather in its environment due to the Jovian magnetosphere and radiation. Indeed, there are alternative views on the radiation-induced S-cycles produced on the surficial molecules that are present on the icy surface; however, S is common to both interpretations. Hence, mass spectrometry should be an essential part of any future payload. The largest S-fractionations are due to microbial reduction and not to thermochemical processes, allowing a test of the hypothesis for the origin of habitable ecosystems. The microbial fractionation of stable S-isotopes argue in favour of penetrators for the survey of the surfaces of both Europa and Ganymede.

Early Earth processes are typically identified through the study of mineralogical, elemental and isotopic features in the rock record, including Precambrian banded iron formations (BIF). However, post-depositional processes often obscure the primary geochemical signals, making the use of BIF as proxies for paleo-seawater and the paleo-biosphere potentially imprecise. Thus, alternative approaches are required to complement the information gained from the rock record in order to fully understand the distinctive biogeochemical processes on ancient Earth. Simulating these conditions in the laboratory is one approach, but this approach can never fully replicate the complexity of a natural environment. Therefore, finding modern environments with a unique set of geochemical and microbiological characteristics to use as analogues for BIF depositional environments can provide invaluable information. In this review, we provide an overview of the chemical, physical and biological parameters of modern, ferruginous lakes that have been used as analogue BIF environments.

The Fourier-transform infrared spectra and the electronic spectra of a series of petroleum fractions of different composition and origins have been studied. Furthermore, these fractions have been modified through the Scholl reaction, a reaction that causes an increase in the aromatic content of the fractions by causing the formation of polycyclic aromatic hydrocarbons (PAHs) or larger PAHs if they were already present in the pristine samples. It is shown that some heavily aromatic petroleum fractions are able to match the emission spectra of the protoplanetary nebula IRAS 22272+5435. Additionally, it is shown that the modified petroleum fractions are able to match the infrared spectrum of anthracite, a high-rank type of coal that has been proposed as the material responsible for the emission of the unidentified infrared bands (UIBs), but which can also be thought of as a model of the kerogen found in meteorites or assumed to be present in cometary nuclei. It is shown that the petroleum fractions considered in this work can be considered even better candidates than coal as a model for the matter present in protoplanetary nebulae and the carrier of the UIBs.

Global extinction and geological events have previously been linked with galactic events such as spiral arm crossings and galactic plane oscillation. The expectation that these are repeating predictable events has led to studies of periodicity in a wide set of biological, geological and climatic phenomena. Using data on carbon isotope excursions, large igneous provinces and impact craters, we identify three time zones of high geological activity which relate to the timings of the passage of the Solar System through the spiral arms. These zones are shown to include a significantly large proportion of high extinction periods. The mass extinction events at the ends of the Ordovician, Permian and Cretaceous occur in the first zone, which contains the predicted midpoints of the spiral arms. The start of the Cambrian, end of the Devonian and end of the Triassic occur in the second zone. The pattern of extinction timing in relation to spiral arm structure is supported by the positions of the superchrons and the predicted speed of the spiral arms. The passage times through an arm are simple multiples of published results on impact and fossil record periodicity and galactic plane half-periods. The total estimated passage time through four arms is 703.8 Myr. The repetition of extinction events at the same points in different spiral arm crossings suggests a common underlying galactic cause of mass extinctions, mediated through galactic effects on geological, solar and extra-solar processes. The two largest impact craters (Sudbury and Vredefort), predicted to have occurred during the early part of the first zone, extend the possible pattern to more than 2000 million years ago.

For many years, it has been assumed that Jupiter has prevented the Earth from being subject to a punishing impact regime that would have greatly hindered the development of life. Here, we present the fourth in a series of dynamical studies investigating this hypothesis. In our earlier work, we examined the effect of Jupiter's mass on the impact rate experienced by the Earth. Here, we extend that approach to consider the influence of Jupiter's orbital eccentricity and inclination on the impact rate from asteroidal bodies and short-period comets. We first considered scenarios in which Jupiter's orbital eccentricity was somewhat higher and somewhat lower than that in our Solar System, for a variety of ‘Jupiter’ masses. We find that Jupiter's orbital eccentricity plays a moderate role in determining the impact flux at Earth, with more eccentric orbits resulting in a noticeably higher impact rate of asteroids than is the case for more circular orbits. This is particularly pronounced at high ‘Jupiter’ masses. For the short-period comets, the same effect is clearly apparent, albeit to a much lesser degree. The flux of short-period comets impacting the Earth is slightly higher for more eccentric Jovian orbits. We also considered scenarios in which Jupiter's orbital inclination was greater than that in our Solar System. Increasing Jupiter's orbital inclination greatly increased the flux of asteroidal impactors upon the Earth. However, at the highest tested inclination, the disruption to the Asteroid belt was so great that the belt would be entirely depleted after an astronomically short period of time. In such a system, the impact flux from asteroid bodies would therefore be very low, after an initial period of intense bombardment. By contrast, the influence of Jovian inclination on impacts from short-period comets was very small. A slight reduction in the impact flux was noted for the moderate and high inclination scenarios considered in this work – the results for inclinations of 5° and 25° were essentially identical.

The principal succession of transformations of a prebiotic microsystem leading to its transition into the primary living state is theoretically substantiated. For the first stage of the succession, a significant change in the external conditions constrains an organic microsystem to leave the current stable state with the following transition into a new stable state through the unstable critical (bifurcation) point. At the bifurcation point the microsystem acquires the original properties without which life cannot exist (self-maintaining heterogeneous structure, incessant fluctuations and rearrangement of molecules, exchange with the surroundings by matter and energy, etc.). During the second stage its unstable state stabilizes relatively by means of the balanced oscillations around the bifurcation point (the paradoxical state of ‘stabilized instability’ appears). The third stage is characterized with the radical turn in the network of chemical reactions: the free energy contribution begins to prevail over the entropy contribution. As a result, constructive transformations proceed faster than destructive transformations. At this stage the key properties of biological organization appear: the ability to concentrate free energy and information, intensified counteraction to external influences, expedient behaviour and persistent self-renovation. On the early Earth, such successive transformation of organic matter occurred in the changeable conditions of a hydrothermal medium. Some new methods for experimental and theoretical research in the origin of life field are suggested.

Bioleaching has been suggested as an alternative to traditional mining techniques in extraterrestrial environments because it does not require extensive infrastructure and bulky hardware. In situ bioleaching of silicate minerals, such as those found on the moon or Mars, has been proposed as a feasible alternative to traditional extraction techniques that require either extreme heat and/or substantial chemical treatment. In this study, we investigated the biotic and abiotic leaching of basaltic rocks (analogues to those found on the moon and Mars) and the mineral ilmenite (FeTiO3) in aqueous environments under acidic (pH ∼ 2.5) and circumneutral pH conditions. The biological leaching experiments were conducted using Acidithiobacillus ferrooxidans, an iron (Fe)-oxidizing bacteria, and Pseudomonas mendocina, an Fe-scavenging bacteria. We found that both strains were able to grow using the Fe(II) derived from the tested basaltic rocks and ilmenite. Although silica leaching rates were the same or slightly less in the bacterial systems with A. ferrooxidans than in the abiotic control systems, the extent of Fe, Al and Ti released (and re-precipitated in new solid phases) was actually greater in the biotic systems. This is likely because the Fe(II) leached from the basalt was immediately oxidized by A. ferrooxidans, and precipitated into Fe(III) phases which causes a change in the equilibrium of the system, i.e. Le Chatelier's principle. Iron(II) in the abiotic experiment was allowed to build up in solution which led to a decrease in its overall release rate. For example, the percentage of Fe, Al and Ti leached (dissolved + reactive mineral precipitates) from the Mars simulant in the A. ferrooxidans experimental system was 34, 41 and 13% of the total Fe, Al and Ti in the basalt, respectively, while the abiotic experimental system released totals of only 11, 25 and 2%. There was, however, no measurable difference in the amounts of Fe and Ti released from ilmenite in the experiments with A. ferrooxidans versus the abiotic controls. P. mendocina scavenged some Fe from the rock/mineral substrates, but the overall amount of leaching was small (<2% of total Fe in rocks) when compared with the acidophilic systems. Although the mineralogy of the tested basaltic rocks was roughly similar, the surface areas of the lunar and Mars simulants varied greatly and thus were possible factors in the overall amount of metals released. Overall, our results indicate that the presence of bacteria does not increase the overall silica leaching rates of basaltic rocks; however, the presence of A. ferrooxidans does lead to enhanced release of Fe, Al and Ti and subsequent sequestration of Fe (and other metals) in Fe(III)-precipitates.