724 research outputs found
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Endolithic colonization of fluid inclusion trails in mineral grains
Many scenarios for the colonization of planetary surfaces by microbial life involve endoliths. This study records microbial mass along fluid inclusion trails (healed microfractures) in quartz grains
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Snow and ice melt flow features on Devon Island, Nunavut, Arctic Canada as possible analogs for recent slope flow features on Mars
Based on morphologic and contextual analogs from Devon Island, Arctic Canada, the recent martian slope flow features reported by Malin and Edgett are reinterpreted as being due not necessarily to groundwater seepage but possibly to snow or ice melt
Role of Meteorite Impacts in the Origin of Life
The conditions, timing, and setting for the origin of life on Earth and whether life exists elsewhere in our solar system and beyond represent some of the most fundamental scientific questions of our time. Although the bombardment of planets and satellites by asteroids and comets has long been viewed as a destructive process that would have presented a barrier to the emergence of life and frustrated or extinguished life, we provide a comprehensive synthesis of data and observations on the beneficial role of impacts in a wide range of prebiotic and biological processes. In the context of previously proposed environments for the origin of life on Earth, we discuss how meteorite impacts can generate both subaerial and submarine hydrothermal vents, abundant hydrothermal–sedimentary settings, and impact analogues for volcanic pumice rafts and splash pools. Impact events can also deliver and/or generate many of the necessary chemical ingredients for life and catalytic substrates such as clays as well. The role that impact cratering plays in fracturing planetary crusts and its effects on deep subsurface habitats for life are also discussed. In summary, we propose that meteorite impact events are a fundamental geobiological process in planetary evolution that played an important role in the origin of life on Earth. We conclude with the recommendation that impact craters should be considered prime sites in the search for evidence of past life on Mars. Furthermore, unlike other geological processes such as volcanism or plate tectonics, impact cratering is ubiquitous on planetary bodies throughout the Universe and is independent of size, composition, and distance from the host star. Impact events thus provide a mechanism with the potential to generate habitable planets, moons, and asteroids throughout the Solar System and beyond
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The influence of shock pressure, pre-shock temperature, and host rock composition on the survival rate of endolithic microorganisms during impact ejection from Mars
Petrographic and biological analysis of shock recovery experiments confirms the possible life transport due to an impact from Mars to Earth
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STONE 6: Artificial Sedimentary Meteorites in Space
The STONE 6 experiment demonstrated the survivability of carbonaceous and microfossiliferous martian analogue sediments during atmospheric re-entry. Doped endoliths died but their carbonised cells remained
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Raman spectroscopy of biologically relevant amino acids under martian condtions
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Raman spectroscopy of amino acids and other biomarkers on Mars
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
Microbial iron reduction on Earth and Mars
The search for life beyond Earth is the driving force behind several future missions
to Mars. An essential task in the lead-up to these missions is a critical assessment of the
habitability for, and feasibility of, life. However, little research has been conducted on this
issue, and our understanding of the plausibility for life on Mars remains unconstrained.
Owing to the anoxic and iron-rich nature of Mars, microbial iron reduction (MIR) represents
a compelling candidate metabolism to operate in the Martian subsurface, past and present.
The objectives of this thesis are to address the feasibility of MIR on Mars by i) better
defining the habitability of MIR on Earth, and ii) assessing the range and availability of
organic electron donors in the subsurface of Earth and Mars.
Samples collected from Mars-relevant environments on Earth were used to initiate
MIR enrichment cultures at 4°C, 15°C and 30°C. Results indicate MIR is widespread in
riverbed and subglacial sediments but not sediments from desert or recent volcanic plains.
The iron-reducing microorganisms in subglacial enrichments are at least psychrotolerant and
in some cases psychrophilc. Culture-independent methods highlighted the changes in
diversity between temperature conditions for subglacial sediments, and indicated that
members of the prolific MIR Geobacteraceae family are common. The genera Geobacter
and Desulfosporosinus are responsible for MIR in the majority of enrichments. Long-term
anoxia and the availability of redox constituents are the major factors controlling MIR in
these environments.
A MIR enrichment culture was unable to use shales and kerogens as the sole source
of electron donors for MIR, despite the presence of known electron donors. Furthermore,
MIR was inhibited by the presence of certain kerogens. The causes of inhibition are
unknown, and are likely to be a combination of chemical and physical factors.
Experiments were conducted to assess the ability of three pure strains and a MIR
enrichment to use non-proteinogenic amino acids common to carbonaceous meteorites as
electron donors for MIR. Results demonstrate that γ-aminobutyric acid served as an electron
donor for the enrichment culture, but no other amino acids supported MIR by this or other
iron-reducing cultures. The D-form of chiral amino acids was found to exert a strong
inhibitory effect, which decreased in line with concentration. Theoretical calculations using
published meteoritic accretion rates onto the surface of Mars indicate that the build up
inhibitory amino acids may place important constrains on habitability over geologic time
scales.
Contamination of a pure strain of Geobacter metallireducens with a strain of
Clostridium revealed a syntrophic relationship between these microorganisms. Anaerobic
heterotrophs are likely to play an important role in maintaining an available supply of
electron donors for MIR and similar chemoorganic metabolisms operating in the subsurface.
This research indicates that MIR remains a feasible metabolism to operate on Mars providing
a readily available redox couple is present. However, given the observed inhibition in the
presence of bulk carbonaceous material and certain amino acids found in meteorites, the use
of extraterrestrial carbonaceous material in the Martian subsurface for microbial iron
reduction is questionable, and should be the focus of future researc
The relevance of prior inclination determination for direct imaging of Earth-like planets
Direct imaging and characterization of extrasolar Earth-like planets is
strongly impacted by the orbital inclination of the planet to be studied, as a
combination of pure geometrical effects and the impact of exozodiacal dust.
Here, we perform simulations to quantify the impact of a priori knowledge of
inclination for the efficiency of a typical coronagraphic or occulter-based
mission. The relative impact and complementarity with prior knowledge of
exozodiacal brightness down to achievable levels is examined and discussed. It
is found that inclination has an even greater impact than the exozodiacal
brightness, though the two have excellent complementarity. We also discuss
different methods for inclination determination, and their respective
applicability to the context of precursor science to an imaging mission. It is
found that if technologically achievable, a combined effort to determine
inclinations and exozodiacal brightnesses with ground-based facilities would
substantially increase the efficiency of a space-based dedicated mission to
image and characterize Earth-like planets.Comment: 9 pages, 5 figures, accepted for publication in MNRA
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