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.

The X-ray emission of the young Sun was much harder and intense than today and might have played a significant role in the evolution of complex organics in protoplanetary environments. We investigate the effects of soft X-rays on tryptophan molecules in aqueous solutions at room temperature. As results of the irradiation experiments we detect several light species indicative of fragmentation, together with large molecular structures such as tryptophan dipeptide and tripeptide. Complexification is more evident in H2O solution than in D2O, probably due to isotopic effects. The abundances of peptides depend on the irradiation dose and decrease with increasing energy deposition. Radicals such as D, OD, H and OH, induced by the X-ray interaction with solvents, play a major role in determining the final products.

Polycyclic aromatic hydrocarbons (PAHs) are robust and abundant molecules in extraterrestrial environments. They are found ubiquitously in the interstellar medium and have been identified in extracts of meteorites collected on Earth. PAHs are important target molecules for planetary exploration missions that investigate the organic inventory of planets, moons and small bodies. This study is part of an interdisciplinary preparation phase to search for organic molecules and life on Mars. We have investigated PAH compounds in desert soils to determine their composition, distribution and stability. Soil samples (Mars analogue soils) were collected at desert areas of Utah in the vicinity of the Mars Desert Research Station (MDRS), in the Arequipa region in Peru and from the Jutland region of Denmark. The aim of this study was to optimize the solid-phase microextraction (SPME) method for fast screening and determination of PAHs in soil samples. This method minimizes sample handling and preserves the chemical integrity of the sample. Complementary liquid extraction was used to obtain information on five- and six-ring PAH compounds. The measured concentrations of PAHs are, in general, very low, ranging from 1 to 60 ng g−1. The texture of soils is mostly sandy loam with few samples being 100 % silt. Collected soils are moderately basic with pH values of 8–9 except for the Salten Skov soil, which is slightly acidic. Although the diverse and variable microbial populations of the samples at the sample sites might have affected the levels and variety of PAHs detected, SPME appears to be a rapid, viable field sampling technique with implications for use on planetary missions.

Carbonate rocks in the Mojave Desert are presented as potential analogues for the carbonates on Mars. Rocks collected from the Little Red Hill site contain iron oxide-bearing coatings that greatly suppress the spectral features due to carbonate of the underlying material and impart a spectral slope. The Mojave Desert was formerly a lush pedogenic soil environment that, over time, transformed into the current arid climate with abundant rock varnish. One niche for microbes in the current desolate environment is inside and underneath the rocks where the microbes profit from solar protection by the iron oxide rock coatings. Carbonates were long predicted to be present on Mars and have recently been detected by instruments on Phoenix and MER and using hyperspectral orbiters such as the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), the Planetary Fourier Spectrometer (PFS) and the Thermal Emission Spectrometer (TES). We describe here the results of a study of carbonate rocks from the Little Red Hill site of the Mojave Desert that includes X-ray diffraction (XRD), chemistry and visible-infrared reflectance spectroscopy. Coatings on the carbonate rocks greatly reduced the strength of the carbonate bands and caused changes in the shape of some bands. We compare these data with a carbonate outcrop at Nili Fossae, Mars. If microbes once inhabited Mars, similar carbonate rocks with iron oxide coatings could have provided a UV-protected niche there as well. Thus, analysis of carbonate-bearing regions on Mars by future landers would be useful sites to search for biosignatures.

Many reasons for why extraterrestrial intelligences might avoid communications with our civilization have been proposed. One possible scenario is that all civilizations follow the lead of some particularly distinguished civilization. This paper will examine the impact the first successful civilization could have on all other subsequent civilizations within its sphere of influence and the ramifications of this as it relates to the Fermi Paradox. Monte Carlo simulation is used to map the inter-arrival times of early civilizations and to highlight the immense epochs of time that the earliest civilizations could have had the Galaxy to themselves.

Phyllosilicate minerals and hydrated sulphate minerals have been positively identified on the surface of Mars. Studies conducted on Earth indicate that micro-organisms influence various geochemical and mineralogical transitions for the sulphate and phyllosilicate minerals. These minerals in turn provide key nutrients to micro-organisms and influence microbial ecology. Therefore, the presence of these minerals in astrobiology studies of Earth–Mars analogue environments could help scientists better understand the types and potential abundance of micro-organisms and/or biosignatures that may be encountered on Mars. Bulk X-ray diffraction of samples collected during the EuroGeoMars 2009 campaign from the Mancos Shale, the Morrison and the Dakota formations near the Mars Desert Research Station in Utah show variable but common sedimentary mineralogy with all samples containing quantities of hydrated sulphate minerals and/or phyllosilicates. Analysis of the clay fractions indicate that the phyllosilicates are interstratified illite–smectites with all samples showing marked changes in the diffraction pattern after ethylene glycol treatment and the characteristic appearance of a solvated peak at ∼17 Å. The smectite phases were identified as montmorillonite and nontronite using a combination of the X-ray diffraction data and Fourier–Transform Infrared Spectroscopy. The most common sulphate mineral in the samples is hydrated calcium sulphate (gypsum), although one sample contained detectable amounts of strontium sulphate (celestine). Carbonates detected in the samples are variable in composition and include pure calcium carbonate (calcite), magnesium-bearing calcium carbonate (dolomite), magnesium, iron and manganese-bearing calcium carbonate (ankerite) and iron carbonate (siderite). The results of these analyses when combined with organic extractions and biological analysis should help astrobiologists and planetary geologists better understand the potential relationships between mineralogy and microbiology for planetary missions.

Long space flights and planetary settlement will require sources of nutrition and chemicals that must be generated in space. This will include not only amino acids and vitamins but also oxygen, all of which can be generated by means of biosynthesis. Synthetic biology has the potential to generate organisms designed for supplying human nutritional needs in space. Photosynthetic microbes may be ideal for this purpose, as they are more efficient per volume cultivated than green plants at conversion of light to chemical energy, biomass and nutritional molecules. In addition, microbes are easier and faster to genetically engineer, facilitating not only design and terrestrial manufacture of organisms optimized for growth and nutrient production in the artificial conditions of space, but superior ability in space to develop organisms suited to newly discovered environments. The rapid ability to adapt and create new microbes to suit new circumstances when in space offers significant potential for risk reduction. Development of sun-driven microbial production of nutritional chemicals would also have terrestrial benefits in commerce and sustainability. A synthetic biology approach to chemical production would not be based on fossil fuels as such fuels do not exist on other planets. This approach would highlight a synergistic relationship between outer space and ‘spaceship earth’, illustrating NASA's role in stimulating technology development with terrestrial application. Two specific approaches deserve consideration: production by traditional photosynthetic microbes, or by the newly appreciated capacity of some bacteria to absorb electric current (e.g. solar panels) to drive metabolism. Palatability and sensory stimulation are a key part of food consumption and could be engineered into microbes. As a first step, NASA should test a bioreactor in which genetically engineered, nutrient-producing photosynthetic bacteria are grown and harvested in space.

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.

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.

Several space agencies and exploration stakeholders have a strong interest in obtaining information on technical and human aspects to prepare for future extra-terrestrial planetary exploration. In this context, the EuroGeoMars campaign, organized with support from the International Lunar Exploration Working Group (ILEWG), the European Space Agency (ESA), the National Aeronautics and Space Administration (NASA) Ames Research Center and partner institutes, was conducted by the crews 76 and 77 in February 2009 in The Mars Society's ‘Mars Desert Research Station’ (MDRS) in Utah.

The EuroGeoMars encompasses two groups of experiments: (1) a series of field science experiments that can be conducted from an extra-terrestrial planetary surface in geology, biology, astronomy/astrophysics and the necessary technology and networks to support these field investigations; (2) a series of human crew-related investigations on crew time organization in a planetary habitat, on the different functions and interfaces of this habitat, and on man–machine interfaces of science and technical equipment.

This paper recalls the objective of the EuroGeoMars project and presents the MDRS and its habitat layout. Social and operational aspects during simulations are described. Technical and operational aspects of biology investigations in the field and in the habitat laboratory are discussed in detail with the focus point set on the polymerase chain reaction (PCR)-based detection of microbial DNA in soil samples.

We collected and analysed soil cores from four geologic units surrounding Mars Desert Research Station (MDRS) Utah, USA, including Mancos Shale, Dakota Sandstone, Morrison formation (Brushy Basin member) and Summerville formation. The area is an important geochemical and morphological analogue to terrains on Mars. Soils were analysed for mineralogy by a Terra X-ray diffractometer (XRD), a field version of the CheMin instrument on the Mars Science Laboratory (MSL) mission (2012 landing). Soluble ion chemistry, total organic content and identity and distribution of microbial populations were also determined. The Terra data reveal that Mancos and Morrison soils are rich in phyllosilicates similar to those observed on Mars from orbital measurements (montmorillonite, nontronite and illite). Evaporite minerals observed include gypsum, thenardite, polyhalite and calcite. Soil chemical analysis shows sulfate the dominant anion in all soils and SO4>>CO3, as on Mars. The cation pattern Na>Ca>Mg is seen in all soils except for the Summerville where Ca>Na. In all soils, SO4 correlates with Na, suggesting sodium sulfates are the dominant phase. Oxidizable organics are low in all soils and range from a high of 0.7% in the Mancos samples to undetectable at a detection limit of 0.1% in the Morrison soils. Minerals rich in chromium and vanadium were identified in Morrison soils that result from diagenetic replacement of organic compounds. Depositional environment, geologic history and mineralogy all affect the ability to preserve and detect organic compounds. Subsurface biosphere populations were revealed to contain organisms from all three domains (Archaea, Bacteria and Eukarya) with cell density between 3.0×106 and 1.8×107 cells ml−1 at the deepest depth. These measurements are analogous to data that could be obtained on future robotic or human Mars missions and results are relevant to the MSL mission that will investigate phyllosilicates on Mars.

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.