The mineralogical characterization of Mars by different exploration missions, provides a new image of the earliest conditions that prevailed on the planet surface. The detection of extensive deposits of phyllosillicates has been considered to be as a result of the production of hydrated silicates through alteration and precipitation under neutral to sub-alkaline conditions. Although extensive deposits of carbonates should precipitate beneath a thick CO₂-bearing atmosphere, only a few outcrops of Mg-rich carbonates have been detected on Mars. Paradoxically those carbonates occur in association with geological units exposed to acidic paleoenvironments. Given such geochemical conditions on Earth, the carbon cycle is intimately associated with life, then, we can assume that the presence or absence of microbial communities should have impacted the distribution of those carbonate compounds on Mars. In this paper, we suggest three potential geobiological scenarios to explain how the emergence of life on Mars would have impacted the carbon cycle and, hence, the formation of carbonates on a planetary scale. Full article

The connection between astrobiology and green chemistry represents a new approach to sustainability of organic matter on asteroids or similar bodies. Green chemistry is chemistry which is environmentally friendly. One obvious way for chemistry to be green is to use water as a solvent, instead of more toxic organic solvents. Many astrobiological reactions occur in the aqueous medium, for example in the prebiotic soup or during the aqueous alteration period on asteroids. Thus any advances in the green organic reactions in water are directly applicable to astrobiology. Another green chemistry approach is to abolish use of toxic solvents. This can be accomplished by carrying out the reactions without a solvent in the solventless or solid-state reactions. The advances in these green reactions are directly applicable to the chemistry on asteroids during the periods when water was not available. Many reactions on asteroids may have been done in the solid mixtures. These reactions may be responsible for a myriad of organic compounds that have been isolated from the meteorites. Full article

Astrobiology, the study of life in the universe, offers profound insights into human sustainability. However, astrobiology is commonly neglected in sustainability research. This paper develops three topics connecting astrobiology to sustainability: constraints on what zones in the universe are habitable, the absence of observations of extraterrestrial civilizations, and the physical fate of the universe. These topics have major implications for our thinking and action on sustainability. While we may not be doomed, we must take certain actions to sustain ourselves in this universe. The topics also suggest that our current sustainability efforts may be of literally galactic importance. Full article

Astrobiology, a new field of research associating the prospects and constraints of prebiotic chemistry, mineralogy, geochemistry, astrophysics, theoretical physics, microbial ecology, etc., is assessed in terms of sustainability through the scientific and social functions it fulfils, and the limits it encounters or strives to overcome. In the same way as sustainable development, astrobiology must also take into account the temporal dimension specific to its field of investigation and examine its underlying conception of Nature. Full article

On Earth, the deep subsurface biosphere of both the oceanic and the continental crust is well known for surviving harsh conditions and environments characterized by high temperatures, high pressures, extreme pHs, and the absence of sunlight. The microorganisms of the terrestrial deep biosphere have an excellent capacity for adapting to changing geochemistry, as the alteration of the crust proceeds and the conditions of their habitats slowly change. Despite an almost complete isolation from surface conditions and the surface biosphere, the deep biosphere of the crustal rocks has endured over geologic time. This indicates that the deep biosphere is a self-sufficient system, independent of the global events that occur at the surface, such as impacts, glaciations, sea level fluctuations, and climate changes. With our sustainable terrestrial subsurface biosphere in mind, the subsurface on Mars has often been suggested as the most plausible place to search for fossil Martian life, or even present Martian life. Since the Martian surface is more or less sterile, subsurface settings are the only place on Mars where life could have been sustained over geologic time. To detect a deep biosphere in the Martian basement, drilling is a requirement. However, near future Mars sample return missions are limited by the mission’s payload, which excludes heavy drilling equipment and restrict the missions to only dig the topmost meter of the Martian soil. Therefore, the sampling and analysis of Martian impact ejecta has been suggested as a way of accessing the deeper Martian subsurface without using heavy drilling equipment. Impact cratering is a natural geological process capable of excavating and exposing large amounts of rock material from great depths up to the surface. Several studies of terrestrial impact deposits show the preservation of pre-impact biosignatures, such as fossilized organisms and chemical biological markers. Therefore, if the Martian subsurface contains a record of life, it is reasonable to assume that biosignatures derived from the Martian subsurface could also be preserved in the Martian impact ejecta. Full article

In the last decades, substantial changes have occurred regarding what scientists consider the limits of habitable environmental conditions. For every extreme environmental condition investigated, a variety of microorganisms have shown that not only can they tolerate these conditions, but that they also often require these extreme conditions for survival. Microbes can return to life even after hundreds of millions of years. Furthermore, a variety of studies demonstrate that microorganisms can survive under extreme conditions, such as ultracentrifugation, hypervelocity, shock pressure, high temperature variations, vacuums, and different ultraviolet and ionizing radiation intensities, which simulate the conditions that microbes could experience during the ejection from one planet, the journey through space, as well as the impact in another planet. With these discoveries, our knowledge about the biosphere has grown and the putative boundaries of life have expanded. The present work examines the recent discoveries and the principal advances concerning the resistance of microorganisms to extreme environmental conditions, and analyzes its contributions to the development of the main themes of astrobiology: the origins of life, the search for extraterrestrial life, and the dispersion of life in the Universe. Full article

Life on a global biosphere basis is substantiated in the form of organics and organisms, and defined as the intermediate forms (briefly expressed as CH₂O) hovering between the reduced (CH₄, methane) and (CO₂, carbon dioxide) ends, different from the classical definition of life as a complex organization maintaining ordered structure and information. Both definitions consider sustenance of life meant as protection of life against chaos through an input of external energy. The CH₂O-life connection is maintained as long as the supply of H and O lasts, which is in turn are provided by the splitting of the water molecule H₂O. Water is split by electricity, as well-known from school-level experiments, and by solar radiation and geothermal heat on a global scale. In other words, the Sun’s radiation and the Earth’s heat as well as radioactivity split water to supply H and O for continued existence of life on the Earth. These photochemical, radiochemical and geothermal processes have influences on the evolution and current composition of the Earth’s atmosphere, compared with those of Venus and Mars, and influences on the planetary climatology. This view of life may be applicable to the “search-for-life in space” and to sustainability assessment of astrobiological habitats. Full article