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Size Limits of Very Small Microorganisms
How small can a free-living organism be? On the surface, this question is straightforward-in principle, the smallest cells can be identified and measured. But understanding what factors determine this lower limit, and addressing the host of other questions that follow on from this knowledge, require a fundamental understanding of the chemistry and ecology of cellular life. The recent report of evidence for life in a martian meteorite and the prospect of searching for biological signatures in intelligently chosen samples from Mars and elsewhere bring a new immediacy to such questions. How do we recognize the morphological or chemical remnants of life in rocks deposited 4 billion years ago on another planet? Are the empirical limits on cell size identified by observation on Earth applicable to life wherever it may occur, or is minimum size a function of the particular chemistry of an individual planetary surface?
These questions formed the focus of a workshop on the size limits of very small organisms, organized by the Steering .Group for the Workshop on Size Limits of Very Small Microorganisms and held on October 22 and 23, 1998. Eighteen invited panelists, representing fields ranging from cell biology and molecular genetics to paleontology and mineralogy, joined with an almost equal number of other participants in a wide-ranging exploration of minimum cell size and the challenge of interpreting micro- and nano-scale features of sedimentary rocks found on Earth or elsewhere in the solar system. This document contains the proceedings of that workshop. It includes position papers presented by the individual panelists, arranged by panel, along with a summary, for each of the four sessions, of extensive roundtable discussions that involved the panelists as well as other workshop participants.
eBook
Perspectives in astrobiology
Astrobiology is the multi-disciplinary field devoted to the investigation of the origin; physical, chemical and environmental limitations; and the distribution in space and time of life on Earth and in the Cosmos. Astrobiology seeks an answer to one of the most fundamental of all questions: Is Life Restricted to Planet Earth or is Life a Cosmic Imperative? Understanding the characteristics, properties, habits and diversity of living organisms on Earth is crucial to determine where and how to search for evidence of life elsewhere. New techniques and methodologies must be developed in order to determine a suitable suite of valid biomarkers that is needed to facilitate the differentiation of abiotic processes from true signatures of life. This is crucial to establish the criteria needed to properly evaluate potential biosignatures in ancient Earth rocks and in a wide variety of Astromaterials. This volume includes papers treating many of these topics. They range from considerations of relict microbial communities of extreme environments to complex organic molecules. Other papers discuss the use of stable isotopes and their biological fractionation as a baseline for evaluating extraterrestrial evidence and the use of chirality and composition of indigenous amino acids for differentiating between terrestrial and extraterrestrial organic matter in Astromaterials. Also treated in this volume are geomorph parallels, sediment patterns, and cyclicities in permafrost sediments of Earth and Mars; the survival of bacteria in space, eclipsing binaries and advanced DNA and protein chip technology for future robotic missions to search for life in the Solar System.
eBook
Extremophilic models for astrobiology: haloarchaeal survival strategies and pigments for remote sensing
Recent progress in extremophile biology, exploration of planetary bodies in the solar system, and the detection and characterization of extrasolar planets are leading to new insights in the field of astrobiology and possible distribution of life in the universe. Among the many extremophiles on Earth, the halophilic Archaea (Haloarchaea) are especially attractive models for astrobiology, being evolutionarily ancient and physiologically versatile, potentially surviving in a variety of planetary environments and with relevance for in situ life detection. Haloarchaea are polyextremophilic with tolerance of saturating salinity, anaerobic conditions, high levels of ultraviolet and ionizing radiation, subzero temperatures, desiccation, and toxic ions. Haloarchaea survive launches into Earth’s stratosphere encountering conditions similar to those found on the surface of Mars. Studies of their unique proteins are revealing mechanisms permitting activity and function in high ionic strength, perchlorates, and subzero temperatures. Haloarchaea also produce spectacular blooms visible from space due to synthesis of red–orange isoprenoid carotenoids used for photoprotection and photorepair processes and purple retinal chromoproteins for phototrophy and phototaxis. Remote sensing using visible and infrared spectroscopy has shown that haloarchaeal pigments exhibit both a discernable peak of absorption and a reflective “green edge”. Since the pigments produce remotely detectable features, they may influence the spectrum from an inhabited exoplanet imaged by a future large space-based telescope. In this review, we focus primarily on studies of two Haloarchaea, Halobacterium sp. NRC-1 and Halorubrum lacusprofundi.
Journal Article
Origin and Evolution of the Universe
Does the universe have the character it has because of design? In this collection of essays first presented at a symposium sponsored by the Canadian Institute for Advanced Research and the Royal Society of Canada, seventeen scientists and philosophers re-examine the \"Argument by Design\" in light of current scientific theories. Scientists in such diverse fields as cosmology, physics, geology, biology, and psychology provide syntheses of the state of their respective disciplines with regard to questions such as the origin or evolution of the universe and of life, the interaction of life and terrestrial environment, and verbal communication in prehumans. Contributions by philosophers cover such areas as arguments for a designer and the question of whether nature's laws and initial conditions could be viewed as \"fine tuned\" for the production of life. Many of the chapters demonstrate the awe-inspiring success of modern science in explaining the universe in terms of fairly straightforward natural laws, countering those versions of the design argument which try to find evidence of God's activities in the supposed failures of scientific laws to cover various phenomena.
eBook
Introduction to the Special Issue - Habitability in the Universe: from the Early Earth to Exoplanets
Europe is also the base of a flourishing exoplanet research community, building on the first discoveries made by European researchers. [...]after more than two decades of research and discussion European Astrobiology has ‘come of age’ and in 2016 will launch its Astrobiology roadmap (www.astromap.eu) which complements that of NASA (astrobiology.nasa.gov/roadmap) and provides a vision for Europe to be a leader in this still new and emerging discipline. ‘First evidence on the role of heavy ions irradiation of meteorites and formamide in the origin of biomolecules’ and the theoretical analysis on ‘Proton-induced Collisions on Potential Prebiotic Species’ by Bacchus-Montabonel. Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their Reservoirs’ a programme to explore habitability in our solar system http://iuap-planet-topers.oma.be. Since Earth provides our only example of a confirmed inhabited planet, the question of how prebiotic molecules assembled to form self-replicating macromolecular systems and how life itself was then able to evolve are central to Astrobiology.
Journal Article
