1,721,037 research outputs found
Decoding the biogeochemical landscape of early life on Earth
No full textConvincing traces of life – biosignatures – have been studied back to approximately 3.5 Ga, suggesting that microbial communities were already sophisticated in their metabolic machinery and distributed through multiple environmental settings. Furthermore, biocoenosis-level ecosystem complexity had evidently already been achieved by 3.5 Ga. Recent evidence from Palaeoarchaean to Neoarchaean (~3.6-2.5 Ga) rocks has further shed light on the co-evolution of Earth and Life: microbial diversity increases together with geological and environmental diversity, with substantial diversification at moments of global environmental revolution such as the development of widespread continental masses or the Great Oxygenation Event. This system of positive feedbacks is reminiscent of the Gaia
Hypothesis
Microbial diversity and biosignatures: an icy moons perspective
Full text linkThe icy moons of the outer Solar System harbor potentially habitable environments for life, however, compared to the terrestrial biosphere, these environments are characterized by extremes in temperature, pressure, pH, and other physico-chemical conditions. Therefore, the search for life on these icy worlds is anchored on the study of terrestrial extreme environments (termed “analogue sites”), which harbor microorganisms at the frontiers of polyextremophily. These so-called extremophiles have been found in areas previously considered sterile: hot springs, hydrothermal vents, acidic or alkaline lakes, hypersaline environments, deep sea sediments, glaciers, and arid areas, amongst others. Such model systems and communities in extreme terrestrial environments may provide important information relevant to the astrobiology of icy bodies, including the composition of potential biological communities and the identification of biosignatures that they may produce. Extremophiles can use either sunlight (phototrophs) or chemical energy (chemotrophs) as energy sources, and different chemical compounds as electron donors or acceptors. Aerobic microorganisms use oxygen (O2) as a terminal electron acceptor, whereas anaerobic microorganisms may use nitrate (NO3-), sulfate (SO42-), carbon dioxide (CO2), Fe(III), or other organic or inorganic molecules during respiration. The phylogenetic diversity of extremophiles is very high, leading to their broad dispersal across the phylogenetic tree of life together with a wide variety in metabolic diversity. Some metabolisms are specific to archaea, for example, methanogenesis, an anaerobic respiration during which methane (CH4) is produced. Also sulfur-reduction performed by some bacteria and archaea is considered as a primitive metabolism which is restricted to anoxic sulfur-rich habitats in nature. Methanogenesis and sulfur reduction are of specific interest for icy moon research as it might be one of the few known terrestrial metabolisms possible on these celestial bodies. Therefore, the adaption of these intriguing microorganisms to extreme conditions will be highlighted within this review
Coupling instrumentation and methodology in the search for traces of life on the early Earth and Mars
Full text linkEvaluating the nature of the earliest, often controversial, traces of life in the geological record (dating to the Palaeoarchaean, up to ~3.5 billion years before the present) is of fundamental relevance for placing constraints on the potential that life emerged on Mars at approximately the same time (the Noachian period). In their earliest histories, the two planets shared many palaeoenvironmental similarities, before the surface of Mars rapidly became inhospitable to life as we know it. Multi-scalar, multi-modal analyses of fossiliferous rocks from the Barberton greenstone belt of South Africa and the East Pilbara terrane of Western Australia are a window onto primitive prokaryotic ecoystems. Complementary petrographic, morphological, (bio)geochemical and nanostructural analyses of chert horizons and the carbonaceous material within using a wide range of techniques – including optical microscopy, SEM-EDS, Raman spectroscopy, PIXE, µCT, laser ablation ICP-MS, high-resolution TEM-based analytical techniques and secondary ion mass spectrometry – can characterise, at scales from macroscopic to nanoscopic, the fossilised biomes of the earliest Earth. These approaches enable the definition of the palaeoenvironments, and potentially metabolic networks, preserved in ancient rocks. Modifying these protocols is necessary for Martian exploration using rovers, since the range and power of space instrumentation is significantly reduced relative to terrestrial laboratories. Understanding the crucial observations possible using highly complementary rover-based payloads is therefore critical in scientific protocols aiming to detect traces of life on Mars
Impacts of Biological and Abiotic Networks. Discussion Leader Introductory Presentation
No full textInternational audienc
Couplage de l'instrumentation et de la méthodologie dans la recherche de traces de vie sur les primitives Terre et Mars
No full textL'évaluation de la nature des traces de vie les plus anciennes, souvent controversées, dans les archives géologiques (datant du Paléoarchéen, jusqu'à environ 3,5 milliards d'années avant nos jours) est d'une importance fondamentale pour imposer des contraintes sur le potentiel d'émergence de la vie sur Mars à environ la même époque (Noachien). Au cours de leurs premières histoires, les deux planètes partageaient de nombreuses similitudes paléoenvironnementales, avant que la surface de Mars ne devienne rapidement inhospitalière à la vie telle que nous la connaissons. Les analyses multiscalaires et multimodales des roches fossilifères de la ceinture de roches vertes de Barberton en Afrique du Sud et du terrain d'East Pilbara en Australie occidentale sont une fenêtre sur les écosystèmes procaryotes primitifs. Analyses complémentaires pétrographiques, morphologiques, (bio)géochimiques et nanostructurales des horizons de Chert et des matériaux carbonés qu'ils contiennent à l'aide d'un large éventail de techniques - notamment la microscopie optique, SEM-EDS, spectroscopie Raman, PIXE, µCT, ablation laser ICP-MS, techniques analytiques basées sur la haute résolution TEM et la spectrométrie de masse des ions secondaires – peuvent caractériser, à des échelles allant du macroscopique au nanoscopique, les biomes fossilisés de la Terre primitive. Ces approches permettent de définir les paléoenvironnements, et potentiellement les réseaux métaboliques, préservés dans les roches anciennes. La modification de ces protocoles est nécessaire pour l'exploration martienne à l'aide de rovers, car la portée et la puissance des instruments spatiaux sont considérablement réduites par rapport aux laboratoires terrestres. Comprendre les observations cruciales possibles à l’aide de charges utiles hautement complémentaires basées sur des rovers est donc essentiel dans les protocoles scientifiques visant à détecter des traces de vie sur Mars.Evaluating the nature of the earliest, often controversial, traces of life in the geological record (dating to the Palaeoarchaean, up to ~3.5 billion years before the present) is of fundamental relevance for placing constraints on the potential that life emerged on Mars at approximately the same time (the Noachian period). In their earliest histories, the two planets shared many palaeoenvironmental similarities, before the surface of Mars rapidly became inhospitable to life as we know it. Multi-scalar, multi-modal analyses of fossiliferous rocks from the Barberton greenstone belt of South Africa and the East Pilbara terrane of Western Australia are a window onto primitive prokaryotic ecoystems. Complementary petrographic, morphological, (bio)geochemical and nanostructural analyses of chert horizons and the carbonaceous material within using a wide range of techniques – including optical microscopy, SEM-EDS, Raman spectroscopy, PIXE, µCT, laser ablation ICP-MS, high-resolution TEM-based analytical techniques and secondary ion mass spectrometry – can characterise, at scales from macroscopic to nanoscopic, the fossilised biomes of the earliest Earth. These approaches enable the definition of the palaeoenvironments, and potentially metabolic networks, preserved in ancient rocks. Modifying these protocols is necessary for Martian exploration using rovers, since the range and power of space instrumentation is significantly reduced relative to terrestrial laboratories. Understanding the crucial observations possible using highly complementary rover-based payloads is therefore critical in scientific protocols aiming to detect traces of life on Mars
Couplage de l'instrumentation et de la méthodologie dans la recherche de traces de vie sur les primitives Terre et Mars
No full textEvaluating the nature of the earliest, often controversial, traces of life in the geological record (dating to the Palaeoarchaean, up to ~3.5 billion years before the present) is of fundamental relevance for placing constraints on the potential that life emerged on Mars at approximately the same time (the Noachian period). In their earliest histories, the two planets shared many palaeoenvironmental similarities, before the surface of Mars rapidly became inhospitable to life as we know it. Multi-scalar, multi-modal analyses of fossiliferous rocks from the Barberton greenstone belt of South Africa and the East Pilbara terrane of Western Australia are a window onto primitive prokaryotic ecoystems. Complementary petrographic, morphological, (bio)geochemical and nanostructural analyses of chert horizons and the carbonaceous material within using a wide range of techniques – including optical microscopy, SEM-EDS, Raman spectroscopy, PIXE, µCT, laser ablation ICP-MS, high-resolution TEM-based analytical techniques and secondary ion mass spectrometry – can characterise, at scales from macroscopic to nanoscopic, the fossilised biomes of the earliest Earth. These approaches enable the definition of the palaeoenvironments, and potentially metabolic networks, preserved in ancient rocks. Modifying these protocols is necessary for Martian exploration using rovers, since the range and power of space instrumentation is significantly reduced relative to terrestrial laboratories. Understanding the crucial observations possible using highly complementary rover-based payloads is therefore critical in scientific protocols aiming to detect traces of life on Mars.L'évaluation de la nature des traces de vie les plus anciennes, souvent controversées, dans les archives géologiques (datant du Paléoarchéen, jusqu'à environ 3,5 milliards d'années avant nos jours) est d'une importance fondamentale pour imposer des contraintes sur le potentiel d'émergence de la vie sur Mars à environ la même époque (Noachien). Au cours de leurs premières histoires, les deux planètes partageaient de nombreuses similitudes paléoenvironnementales, avant que la surface de Mars ne devienne rapidement inhospitalière à la vie telle que nous la connaissons. Les analyses multiscalaires et multimodales des roches fossilifères de la ceinture de roches vertes de Barberton en Afrique du Sud et du terrain d'East Pilbara en Australie occidentale sont une fenêtre sur les écosystèmes procaryotes primitifs. Analyses complémentaires pétrographiques, morphologiques, (bio)géochimiques et nanostructurales des horizons de Chert et des matériaux carbonés qu'ils contiennent à l'aide d'un large éventail de techniques - notamment la microscopie optique, SEM-EDS, spectroscopie Raman, PIXE, µCT, ablation laser ICP-MS, techniques analytiques basées sur la haute résolution TEM et la spectrométrie de masse des ions secondaires – peuvent caractériser, à des échelles allant du macroscopique au nanoscopique, les biomes fossilisés de la Terre primitive. Ces approches permettent de définir les paléoenvironnements, et potentiellement les réseaux métaboliques, préservés dans les roches anciennes. La modification de ces protocoles est nécessaire pour l'exploration martienne à l'aide de rovers, car la portée et la puissance des instruments spatiaux sont considérablement réduites par rapport aux laboratoires terrestres. Comprendre les observations cruciales possibles à l’aide de charges utiles hautement complémentaires basées sur des rovers est donc essentiel dans les protocoles scientifiques visant à détecter des traces de vie sur Mars
Impacts of Biological and Abiotic Networks. Discussion Leader Introductory Presentation
No full textInternational audienc
Couplage de l'instrumentation et de la méthodologie dans la recherche de traces de vie sur les primitives Terre et Mars
No full textEvaluating the nature of the earliest, often controversial, traces of life in the geological record (dating to the Palaeoarchaean, up to ~3.5 billion years before the present) is of fundamental relevance for placing constraints on the potential that life emerged on Mars at approximately the same time (the Noachian period). In their earliest histories, the two planets shared many palaeoenvironmental similarities, before the surface of Mars rapidly became inhospitable to life as we know it. Multi-scalar, multi-modal analyses of fossiliferous rocks from the Barberton greenstone belt of South Africa and the East Pilbara terrane of Western Australia are a window onto primitive prokaryotic ecoystems. Complementary petrographic, morphological, (bio)geochemical and nanostructural analyses of chert horizons and the carbonaceous material within using a wide range of techniques – including optical microscopy, SEM-EDS, Raman spectroscopy, PIXE, µCT, laser ablation ICP-MS, high-resolution TEM-based analytical techniques and secondary ion mass spectrometry – can characterise, at scales from macroscopic to nanoscopic, the fossilised biomes of the earliest Earth. These approaches enable the definition of the palaeoenvironments, and potentially metabolic networks, preserved in ancient rocks. Modifying these protocols is necessary for Martian exploration using rovers, since the range and power of space instrumentation is significantly reduced relative to terrestrial laboratories. Understanding the crucial observations possible using highly complementary rover-based payloads is therefore critical in scientific protocols aiming to detect traces of life on Mars.L'évaluation de la nature des traces de vie les plus anciennes, souvent controversées, dans les archives géologiques (datant du Paléoarchéen, jusqu'à environ 3,5 milliards d'années avant nos jours) est d'une importance fondamentale pour imposer des contraintes sur le potentiel d'émergence de la vie sur Mars à environ la même époque (Noachien). Au cours de leurs premières histoires, les deux planètes partageaient de nombreuses similitudes paléoenvironnementales, avant que la surface de Mars ne devienne rapidement inhospitalière à la vie telle que nous la connaissons. Les analyses multiscalaires et multimodales des roches fossilifères de la ceinture de roches vertes de Barberton en Afrique du Sud et du terrain d'East Pilbara en Australie occidentale sont une fenêtre sur les écosystèmes procaryotes primitifs. Analyses complémentaires pétrographiques, morphologiques, (bio)géochimiques et nanostructurales des horizons de Chert et des matériaux carbonés qu'ils contiennent à l'aide d'un large éventail de techniques - notamment la microscopie optique, SEM-EDS, spectroscopie Raman, PIXE, µCT, ablation laser ICP-MS, techniques analytiques basées sur la haute résolution TEM et la spectrométrie de masse des ions secondaires – peuvent caractériser, à des échelles allant du macroscopique au nanoscopique, les biomes fossilisés de la Terre primitive. Ces approches permettent de définir les paléoenvironnements, et potentiellement les réseaux métaboliques, préservés dans les roches anciennes. La modification de ces protocoles est nécessaire pour l'exploration martienne à l'aide de rovers, car la portée et la puissance des instruments spatiaux sont considérablement réduites par rapport aux laboratoires terrestres. Comprendre les observations cruciales possibles à l’aide de charges utiles hautement complémentaires basées sur des rovers est donc essentiel dans les protocoles scientifiques visant à détecter des traces de vie sur Mars
Fossilization of Bacteria and The Implications for The Search for Early Life Forms. Biosignatures In Astrobiology Missions to Mars
No full textInternational audienceThroughout the first few billion years of its history, microbial cells were the only life-forms on Earth and present the only life-forms that could have once existed or still exist on Mars. Our understanding of the formation of the signatures of microbial life-forms (biosignatures) comes from experimental fossilization studies, together with the detailed investigation of their remains throughout the preserved geological history of the Earth. We here resume mechanisms for the preservation of microbial biosignatures and review a selection of the highly diverse and well-preserved biota from the early history of the Earth. Our understanding of early life is informative for the search for life on Mars, presenting a paleontological and philosophical analogue against which putative signs of Martian life will need to be tested. Significant differences in the conditions of habitability between Mars and the Earth indicate that only primitive chemotrophic life-forms could have inhabited, or still inhabit, the Red Planet, and this may set a unique set of challenges for the proof of Martian biosignatures. We conclude by briefly outlining the findings of several decades of past and present missions of astrobiological interest to Mars and consider what additional information future missions could bring
Fossilization of Bacteria and The Implications for The Search for Early Life Forms. Biosignatures In Astrobiology Missions to Mars
No full textInternational audienceThroughout the first few billion years of its history, microbial cells were the only life-forms on Earth and present the only life-forms that could have once existed or still exist on Mars. Our understanding of the formation of the signatures of microbial life-forms (biosignatures) comes from experimental fossilization studies, together with the detailed investigation of their remains throughout the preserved geological history of the Earth. We here resume mechanisms for the preservation of microbial biosignatures and review a selection of the highly diverse and well-preserved biota from the early history of the Earth. Our understanding of early life is informative for the search for life on Mars, presenting a paleontological and philosophical analogue against which putative signs of Martian life will need to be tested. Significant differences in the conditions of habitability between Mars and the Earth indicate that only primitive chemotrophic life-forms could have inhabited, or still inhabit, the Red Planet, and this may set a unique set of challenges for the proof of Martian biosignatures. We conclude by briefly outlining the findings of several decades of past and present missions of astrobiological interest to Mars and consider what additional information future missions could bring
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