1,721,231 research outputs found
In situ NanoSIMS geochemistry of an exceptionally well preserved Paleoarchaean carbonaceous microfossils a key for planetary habitability
No full textAnalytical methods to distinguishing biotic from abiotic features are crucially important for search evidence
of life that could include problematic and fragmentary organic remnants in ancient terrestrial rocks as well as
in extra-terrestrial materials. The NanoSIMS is the only instrument that has the capability of measuring
isotope ratios accurately from very small sample volumes.
This project aims to establish by using the TA3-NanoSIMS the biogenicity of unique 3.41-3.33-billion-year-old
microfilaments discovered in one of the oldest outcrops, which include the few known signs of early life.
These microfilaments were found in a vein-infill hydrothermal system. The objectives are to obtain by
NanoSIMS in situ measurements, the C-Si-O isotope ratios of these carbonaceous filaments and the associated
clots and host Si-matrix.
The C-isotope ratio would elucidate the biological nature of the filaments and possibly infer their metabolism,
and would help in discerning if clots are abiotic or genuine fossil remains. The Si-O isotope ratio of the host
Si-matrix would constrain the temperature of hydrothermal fluids and help in the paleoenvironmental
reconstruction of a primordial lifes habitat.
Hydrothermal systems are crucial targets in search for early life, and likely were the prevailing habitats of
Earth at its beginning. A better knowledge of early terrestrial paleoenvironments could have important
implications for elsewhere understanding the planetary evolution and habitability
NANOCRYSTALS AS BIOSIGNATURES IN 3.5 BILLION YEARS OLD MICROBIAL REMAINS
No full textNatural, spherical aggregates of carbonaceous materials (CM), called clots (average diameter: ca. 200 microns), embedded in ancient chert (silica) host matrix represent the most common type of the ancient CM with purported biological origin on Earth. However, to date they have received scarcity of attention and are only been qualitatively described. The clots object of this study, have the same age of the oldest know fossils know.
The aim of the proposed research project is to characterize at the micro-nano-atomic-scale, the different generation of natural, spherical aggregation of carbonaceous materials that can be recognized from ca. 3.5-3.3 billion years old rocks from Barberton greenstone belt in South Africa, to demonstrate their biological (or abiotic?) origin, and, possibly, deciphering crucial aspects of early life. Mineral nano-phases, trace elements and molecular information can be used as biological signals when associated to morphological features coming from the right geological context. Therefore, versatile in situ analytical techniques borrowed from nanotechnology become of critical importance as they can provide morphological, structural, chemical, and mineralogical signatures to recognize abiotic microfossil-like structures, identify fossil microorganisms, demonstrate their antiquity, and decipher their activities and host environments. The complete characterization of the CM of the clotted textures will be crucial to explore their role in Archaean (4-2.5 billion years) geochemical and biogeochemical processes, since they represent an important and unknown fraction of the ancient carbonaceous materials.
This represent a novel, interdisciplinary study (across geobiology, nanotechnology and material sciences) as investigates a type of ancient CM, that has so far not been subjected to any detailed geo-biological researches, but that can be demonstrated to be associated to life
SEARCHING FOR BIOSIGNATURES IN ANCIENT CARBONACEOUS MATTER AS EVIDENCE OF EARLY LIFE
No full textNatural, spherical aggregates of carbonaceous materials (CM), called clots (average diameter: ca. 200 microns), embedded in ancient chert (silica) host matrix represent the most common type of the ancient CM with purported biological origin on Earth. However, to date they have received scarcity of attention and are only been qualitatively described. The clots object of this study, have the same age of the oldest know fossils know.
The aim of the proposed research project is to characterize at the micro-nano-atomic-scale, the different generation of natural, spherical aggregation of carbonaceous materials that can be recognized from ca. 3.5-3.3 billion years old rocks from Barberton greenstone belt in South Africa, to demonstrate their biological (or abiotic?) origin, and, possibly, deciphering crucial aspects of early life. Mineral nano-phases, trace elements and molecular information can be used as biological signals when associated to morphological features coming from the right geological context. Therefore, versatile in situ analytical techniques borrowed from nanotechnology become of critical importance as they can provide morphological, structural, chemical, and mineralogical signatures to recognize abiotic microfossil-like structures, identify fossil microorganisms, demonstrate their antiquity, and decipher their activities and host environments. The complete characterization of the CM of the clotted textures will be crucial to explore their role in Archaean (4-2.5 billion years) geochemical and biogeochemical processes, since they represent an important and unknown fraction of the ancient carbonaceous materials.
This represent a novel, interdisciplinary study (across geobiology, nanotechnology and material sciences) as investigates a type of ancient CM, that has so far not been subjected to any detailed geo-biological researches, but that can be demonstrated to be associated to life. I am highly motivated and interested in developing this interdisciplinary project that is drawn on my experience and expertise on microbial palaeontology, and the expert microscopists and material scientists involved in CERIC-ERIC program. I am persuaded that the use of high-resolution and new technology in defining new biosignatures in microbial palaeontology (and astrobiology) is the right approach. Therefore, this collaboration will guarantee the success of this project
Diverse communities of Bacteria and Archaea flourished in Palaeoarchaean (3.5-3.3 Ga) microbial mats
Full text linkLimited taxonomic classification is possible for Archaean microbial mats and this is a fundamental limitation in constraining the nature of early life. Here, we apply Fourier Transform Infrared spectroscopy (FTIR), a powerful tool for identifying vibrational motions attributable to specific molecules and functional groups, to characterise fossilised biopolymers in 3.5-3.3 Ga microbial mats from the Barberton greenstone belt (South Africa). Using multiple statistical methods, we show that microbial mats from four Palaeoarchaean horizons exhibit significant differences in taxonomically informative aliphatic contents, despite uniformly high aromaticity. This diversity can only be explained by precursor biological heterogeneity since all horizons underwent similar grades of metamorphism. Low methylene to end-methyl (CH2/CH3) absorbance ratios in mats from the 3.472 Ga Middle Marker horizon signify short, highly branched n-alkanes interpreted as isoprenoid chains forming archaeal membranes. Mats from the 3.45 Ga Hooggenoeg Chert H5c, 3.334 Ga Footbridge Chert, and 3.33 Ga Josefsdal Chert exhibit higher CH2/CH3 ratios suggesting longer, unbranched fatty acids from bacterial membrane lipid precursors. Absorbance ratios of end-methyl to methylene (CH3/CH2) in Josefsdal Chert and Footbridge Chert mats yield a range of values (0.20-0.80) suggesting mixed bacterial and archaeal architect communities based on comparison with modern examples. Low R3/2 values (< 0.5) in Hooggenoeg mats denote dominantly Bacteria, whereas high (0.78-1.25) R3/2 ratios in the Middle Marker mats identify Archaea. This exceptional preservation reflects early, rapid silicification preventing the alteration of biogeochemical signals inherited from the precursor biomass. Since silicification commenced during the lifetime of the microbial mat, the reported FTIR signals estimate the affinities of the architect community and may be used in the reconstruction of Archaean ecosystems. Taken together, these results show statistically significant distinctions and similarities demonstrating that Bacteria and Archaea flourished together in Earth’s earliest ecosystems
Search for stomatolite-like structures in the martian environment
No full textAssuming that exchanges of forms of life could have occurred between Mars and Earth, we investigate where and how a future mission could detect stromatolite-like structures similar to the terrestrial ones. In the terrestrial fossil record, the presence of laminated structures may derive from biologic processes such as those originating stromatolites. Stromatolites are finely laminated, lithified microbial structures that may preserve traces of microorganisms (primarily prokaryotes) widespread in suitable aquatic habitats. We propose to select the sites where such laminated Mars rocks could exist, by an appropriate radar system
Astrobiology vs Geology investigations: good practices in the framework of planetary missions
Full text linkThe deep link between biosignature identification and geological setting is at the foundation of astrobiological investigations on Earth and should be the same for planetary exploration. In order to constrain the analogy between the potential Earth analogue and the planetary setting, an increasingly detailed sets of analyses in an increasingly detailed scale should be performed in parallel between the Earth and the interested planetary surface. Ultimately, geological investigations are critical to correctly plan remote and in situ planetary missions aimed at assessing the habitability potential of a specific planet/setting. This is even more essential if a sample return mission is expected, in order to collect THE right samples and not just stones
Correlative microspectroscopy of biogenic fabrics in Proterozoic silicified stromatolites
Full text linkQuestions surrounding the biogenicity of ancient stromatolites have perplexed geobiologists for decades. Abiotic processes can produce superficially stromatolite-like structures; moreover, stromatolites frequently fail to preserve organic materials and cellular traces of their microbial architects. Using spatially correlated optical and electron microscopy coupled with Raman and FTIR microspectroscopy, we show that silicified stromatolites from the Tonian Skillogalee Dolomite (Flinders Ranges, South Australia) contain exceptionally well-preserved microbial mat fragments and microbially induced sedimentary structures. These organic-rich layers exhibit mat-like laminations with low degrees of inheritance and reflect interactions between microbial communities and their environments, i.e. growth, sediment trapping and binding, and reactions to early diagenesis, and are inconsistent with abiotic formation. Although accounting for a minor proportion of the volume of the stromatolites, these kerogenous relics are demonstrably syngenetic and comprise aromatic and aliphatic organic materials, likely
preserved due to early and rapid silicification. Constraining the origins of such lamina-scale features can elucidate relationships between morphogenesis and diagenesis to assist the resolution of controversies surrounding stromatolite biogenicity in deep time
Chemosynthetic microbialites in the Devonian carbonate mounds of Hamar Laghdad (Anti-Atlas, Morocco)
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