A biosignature (sometimes called chemical fossil or molecular fossil) is any substance – such as an element, isotope, or molecule – or phenomenon that provides scientific evidence of past or present life. Measurable attributes of life include its complex physical or chemical structures and its use of free energy and the production of biomass and wastes. A biosignature can provide evidence for living organisms outside the Earth and can be directly or indirectly detected by searching for their unique byproducts.
In general, biosignatures can be grouped into ten broad categories:
Isotope patterns: Isotopic evidence or patterns that require biological processes.
Chemistry: Chemical features that require biological activity.
Organic matter: Organics formed by biological processes.
Minerals: Minerals or biomineral-phases whose composition and/or morphology indicate biological activity (e.g., biomagnetite).
Microscopic structures and textures: Biologically formed cements, microtextures, microfossils, and films.
Macroscopic physical structures and textures: Structures that indicate microbial ecosystems, biofilms (e.g., stromatolites), or fossils of larger organisms.
Temporal variability: Variations in time of atmospheric gases, reflectivity, or macroscopic appearance that indicate the presence of life.
Surface reflectance features: Large-scale reflectance features due to biological pigments, which could be detected remotely.
Atmospheric gases: Gases formed by metabolic and/or aqueous processes, which may be present on a planet-wide scale.
Technosignatures: Signatures that indicate a technologically advanced civilization.
Determining if a potential biosignature is worth being investigated is a fundamentally complicated process. Scientists must consider any and every possible alternate explanation before concluding that something is a true biosignature. This includes investigating the minute details that make other planets unique and being able to understand when there is a deviation from the expected non-biological processes present on a planet.
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Understanding process and role of biomineralization (minerals formed by living organisms) in context of Earth's evolution,global chemical cycles, climatic changes and remediation.
Explores geochemical modeling applications, including stability diagrams, selenium speciation, mineral precipitation estimation, and redox disequilibrium.
Planetary habitability is the measure of a planet's or a natural satellite's potential to develop and maintain environments hospitable to life. Life may be generated directly on a planet or satellite endogenously or be transferred to it from another body, through a hypothetical process known as panspermia. Environments do not need to contain life to be considered habitable nor are accepted habitable zones (HZ) the only areas in which life might arise.
Astrobiology is a scientific field within the life and environmental sciences that studies the origins, early evolution, distribution, and future of life in the universe by investigating its deterministic conditions and contingent events. As a discipline, astrobiology is founded on the premise that life may exist beyond Earth. Research in astrobiology comprises three main areas: the study of habitable environments in the Solar System and beyond, the search for planetary biosignatures of past or present extraterrestrial life, and the study of the origin and early evolution of life on Earth.
Lithotrophs are a diverse group of organisms using an inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis (e.g., carbon dioxide fixation) or energy conservation (i.e., ATP production) via aerobic or anaerobic respiration. While lithotrophs in the broader sense include photolithotrophs like plants, chemolithotrophs are exclusively microorganisms; no known macrofauna possesses the ability to use inorganic compounds as electron sources.
In recent years, many efforts have been made to find alternative renewable energy sources that can ideally replace the use of fossil fuels in all aspects. One of the new emerging energy technologies is the bioelectrochemical system, of which two types are ...
The probability of detecting technosignatures (i.e., evidence of technological activity beyond Earth) increases with their longevity, or the time interval over which they manifest. Therefore, the assumed distribution of longevities has some bearing on the ...
Kinetic information extracted from biochemical methane potential (BMP) tests is often reported but its value is unclear. Inter-laboratory reproducibility provides a useful indication of its value. Here we extracted estimates of the first-order rate constan ...