V. K. Pearson

Contamination by sesquiterpenoid derivatives in the Orgueil carbonaceous chondrite

The free organic components of the Orgueil carbonaceous chondrite have been the subject of much controversy. Several proposals for their source have been put forward including extraterrestrial abiotic processes, extraterrestrial life and terrestrial contamination. In this study we have analysed the free components to assess their distribution and possible sources. Compounds suggestive of terrestrial contamination by essential plant oil derivatives are evident. Their distribution suggests a source such as cleaning products, disinfectant and air-freshener, where they are present in refined form. This study strongly highlights the need for extreme care when interpreting organic data from meteorites with long curational histories. Future meteorites falls and extraterrestrial sample returns should be stored so as to avoid being compromised by similar terrestrial substances.

Institutional change for improving accessibility in the design and delivery of distance learning – the role of faculty accessibility specialists at The Open University

The Open University (OU) has an established infrastructure for supporting disabled students. Historically, the thrust of this has focused on providing accessible adjustments post-production. In 2012, the OU implemented securing greater accessibility (SeGA) to raise awareness and bring about an institutional change to curriculum design so that the needs of all students, including disabled students, are taken into account from the outset of module design and production. A core component of SeGA is the introduction of faculty accessibility specialists (AS). This case study discusses the successes and challenges for AS in motivating and supporting production teams in the adoption of inclusive anticipatory practices to make new curriculum accessible. It also outlines the process of reasonable adjustment during presentation. It shows how collaborative working between AS has helped standardise design and production processes for accessibility, principles with wider relevance for supporting disabled students in other higher education institutions.

Molecular, isotopic and in situ analytical approaches to the study of meteoritic organic material

Organic materials isolated from carbonaceous meteorites provide us with a record of pre-biotic chemistry in the early Solar System. Molecular, isotopic and in situ studies of these materials suggest that a number of extraterrestrial environments have contributed to the inventory of organic matter in the early Solar System including interstellar space, the Solar nebula and meteorite parent bodies. There are several difficulties that have to be overcome in the study of the organic constituents of meteorites. Contamination by terrestrial biogenic organic matter is an ever-present concern and a wide variety of contaminant molecules have been isolated and identified including essential plant oils, derived from either biological sources or common cleaning products, and aliphatic hydrocarbons, most probably derived from petroleum-derived pollutants. Only 25 % of the organic matter in carbonaceous chondrites is amenable to extraction with organic solvents ; the remainder is present as a complex macromolecular aromatic network that has required the development of analytical approaches that can yield structural and isotopic information on this highly complex material. Stable isotopic studies have been of paramount importance in understanding the origins of meteoritic organic matter and have provided evidence for the incorporation of interstellar molecules within meteoritic material. Extending isotopic studies to the molecular level is yielding new insights into both the sources of meteoritic organic matter and the processes that have modified it. Organic matter in meteorites is intimately associated with silicate minerals and the in situ examination of the relationships between organic and inorganic components is crucial to our understanding of the role of asteroidal processes in the modification of organic matter and, in particular, the role of water as both a solvent and a reactant on meteorite parent bodies. Received 1 July 2004, accepted 1 September 2004

Nitrate-Dependent Iron Oxidation: A Potential Mars Metabolism

This work considers the hypothetical viability of microbial nitrate-dependent Fe2+ oxidation (NDFO) for supporting simple life in the context of the early Mars environment. This draws on knowledge built up over several decades of remote and in situ observation, as well as recent discoveries that have shaped current understanding of early Mars. Our current understanding is that certain early martian environments fulfill several of the key requirements for microbes with NDFO metabolism. First, abundant Fe2+ has been identified on Mars and provides evidence of an accessible electron donor; evidence of anoxia suggests that abiotic Fe2+ oxidation by molecular oxygen would not have interfered and competed with microbial iron metabolism in these environments. Second, nitrate, which can be used by some iron oxidizing microorganisms as an electron acceptor, has also been confirmed in modern aeolian and ancient sediment deposits on Mars. In addition to redox substrates, reservoirs of both organic and inorganic carbon are available for biosynthesis, and geochemical evidence suggests that lacustrine systems during the hydrologically active Noachian period (4.1–3.7 Ga) match the circumneutral pH requirements of nitrate-dependent iron-oxidizing microorganisms. As well as potentially acting as a primary producer in early martian lakes and fluvial systems, the light-independent nature of NDFO suggests that such microbes could have persisted in sub-surface aquifers long after the desiccation of the surface, provided that adequate carbon and nitrates sources were prevalent. Traces of NDFO microorganisms may be preserved in the rock record by biomineralization and cellular encrustation in zones of high Fe2+ concentrations. These processes could produce morphological biosignatures, preserve distinctive Fe-isotope variation patterns, and enhance preservation of biological organic compounds. Such biosignatures could be detectable by future missions to Mars with appropriate instrumentation.

The Microbial Community of a Terrestrial Anoxic Inter-Tidal Zone: A Model for Laboratory-Based Studies of Potentially Habitable Ancient Lacustrine Systems on Mars

Evidence indicates that Gale crater on Mars harboured a fluvio-lacustrine environment that was subjected to physio-chemical variations such as changes in redox conditions and evaporation with salinity changes, over time. Microbial communities from terrestrial environmental analogues sites are important for studying such potential habitability environments on early Mars, especially in laboratory-based simulation experiments. Traditionally, such studies have predominantly focused on microorganisms from extreme terrestrial environments. These are applicable to a range of Martian environments; however, they lack relevance to the lacustrine systems. In this study, we characterise an anoxic inter-tidal zone as a terrestrial analogue for the Gale crater lake system according to its chemical and physical properties, and its microbiological community. The sub-surface inter-tidal environment of the River Dee estuary, United Kingdom (53°21′15.40″ N, 3°10′24.95″ W) was selected and compared with available data from Early Hesperian-time Gale crater, and temperature, redox, and pH were similar. Compared to subsurface ‘groundwater’-type fluids invoked for the Gale subsurface, salinity was higher at the River Dee site, which are more comparable to increases in salinity that likely occurred as the Gale crater lake evolved. Similarities in clay abundance indicated similar access to, specifically, the bio-essential elements Mg, Fe and K. The River Dee microbial community consisted of taxa that were known to have members that could utilise chemolithoautotrophic and chemoorganoheterotrophic metabolism and such a mixed metabolic capability would potentially have been feasible on Mars. Microorganisms isolated from the site were able to grow under environment conditions that, based on mineralogical data, were similar to that of the Gale crater’s aqueous environment at Yellowknife Bay. Thus, the results from this study suggest that the microbial community from an anoxic inter-tidal zone is a plausible terrestrial analogue for studying habitability of fluvio-lacustrine systems on early Mars, using laboratory-based simulation experiments.

Determination of Geochemical Bio-Signatures in Mars-Like Basaltic Environments

Bio-signatures play a central role in determining whether life existed on early Mars. Using a terrestrial basalt as a compositional analog for the martian surface, we applied a combination of experimental microbiology and thermochemical modeling techniques to identify potential geochemical bio-signatures for life on early Mars. Laboratory experiments were used to determine the short-term effects of biota on the dissolution of terrestrial basalt, and the formation of secondary alteration minerals. The chemoorganoheterotrophic bacterium, Burkholderia sp. strain B_33, was grown in a minimal growth medium with and without terrestrial basalt as the sole nutrient source. No growth was detected in the absence of the basalt. In the presence of basalt, during exponential growth, the pH decreased rapidly from pH 7.0 to 3.6 and then gradually increased to a steady-state of equilibrium of between 6.8 and 7.1. Microbial growth coincided with an increase in key elements in the growth medium (Si, K, Ca, Mg, and Fe). Experimental results were compared with theoretical thermochemical modeling to predict growth of secondary alteration minerals, which can be used as bio-signatures, over a geological timescale. We thermochemically modeled the dissolution of the basalt (in the absence of biota) in very dilute brine at 25°C, 1 bar; the pH was buffered by the mineral dissolution and precipitation reactions. Preliminary results suggested that at the water to rock ratio of 1 × 107, zeolite, hematite, chlorite, kaolinite, and apatite formed abiotically. The biotic weathering processes were modeled by varying the pH conditions within the model to adjust for biologic influence. The results suggested that, for a basaltic system, the microbially-mediated dissolution of basalt would result in “simpler” secondary alteration, consisting of Fe-hydroxide and kaolinite, under conditions where the abiotic system would also form chlorite. The results from this study demonstrate that, by using laboratory-based experiments and thermochemical modeling, it is possible to identify secondary alteration minerals that could potentially be used to distinguish between abiotic and biotic weathering processes on early Mars. This work will contribute to the interpretation of data from past, present, and future life detection missions to Mars.