Exobiology

During the last decade, there was a paradigm-shift in order to consider terrestrial planets within liquid-water habitable zones (LW-HZ) around M stars, as suitable places for the emergence and evolution of life. Here we analyze the influence of UV boundary conditions to three planetary systems around dM (HIP 74995, HIP 109388 and HIP 113020). We apply our model of UV habitable zone (UV-HZ) (Buccino et al. 2006) to these cases and show that during the quiescent UV output there would not be enough UV radiation within the LW-HZ in order to trigger biogenic processes. We also analyze the cases of two other M flare stars and show that the flares of moderate intensity could provide the necessary energy to trigger those biogenic processes, while the strong flares not necessary rule-out the possibility of life-bearing planets.

The results of the biology and organic chemistry experiments carried aboard the Viking landers seem to rule out the possibility of life on Mars. However, we present a possible model of Martian ecology which is based on the premise that Martian life could be endolithic, and thus missed by the Viking biology experiments. This model is based, in part, on the endolithic microbiota found in the dry valleys of Antarctica. In addition, we combine our model with a previously described model which suggests that Mars may go through ice ages and periods of relatively mild climate.

Ice-covered ocean worlds possess diverse energy sources and associated mechanisms that are capable of driving significant seismic activity, but to date no measurements of their seismic activity have been obtained. Such investigations could reveal the transport properties and radial structures, with possibilities for locating and characterizing trapped liquids that may host life and yielding critical constraints on redox fluxes and thus on habitability. Modeling efforts have examined seismic sources from tectonic fracturing and impacts. Here, we describe other possible seismic sources, their associations with science questions constraining habitability, and the feasibility of implementing such investigations. We argue, by analogy with the Moon, that detectable seismic activity should occur frequently on tidally flexed ocean worlds. Their ices fracture more easily than rocks and dissipate more tidal energy than the <1 GW of the Moon and Mars. Icy ocean worlds also should create les...

We have synthesized inorganic micron-sized filaments, whose microstucture consists of silica-coated nanometer-sized carbonate crystals, arranged with strong orientational order. They exhibit noncrystallographic, curved, helical morphologies, reminiscent of biological forms. The filaments are similar to supposed cyanobacterial microfossils from the Precambrian Warrawoona chert formation in Western Australia, reputed to be the oldest terrestrial microfossils. Simple organic hydrocarbons, whose sources may also be abiotic and indeed inorganic, readily condense onto these filaments and subsequently polymerize under gentle heating to yield kerogenous products. Our results demonstrate that abiotic and morphologically complex microstructures that are identical to currently accepted biogenic materials can be synthesized inorganically.

Archaeology might be defined simply as the study of 'the human altered world'. Until recently, traces of humanity's past could have only been found on Earth. But, as our influence continues to expand beyond, we must consider human activities and human-made objects in space and how they—as extensions of ourselves—impact other worlds and the spaces between. This is 'space archaeology'. Features interviews with five activists and innovators in the research and education of outer space from the perspective of archaeology and anthropology.

Ultraviolet radiation is known to inhibit photosynthesis, induce DNA destruction and cause damage to a wide variety of proteins and lipids. In particular, UV radiation between 200-300 nm becomes energetically very damaging to most of the terrestrial biological systems. On the other hand, UV radiation is usually considered one of the most important energy source on the primitive Earth for the synthesis of many biochemical compounds and, therefore, essential for several biogenesis processes. In this work, we use these properties of the UV radiation to define the boundaries of an ultraviolet habitable zone. We also analyze the evolution of the UV habitable zone during the main sequence stage of the star. We apply these criteria to study the UV habitable zone for those extrasolar planetary systems that were observed by the International Ultraviolet Explorer (IUE). We analyze the possibility that extrasolar planets and moons could be suitable for life, according to the UV constrains pres...

There is no broadly accepted definition of 'life.' Suggested definitions face problems, often in the form of robust counter-examples. Here we use insights from philosophical investigations into language to argue that defining 'life' currently poses a dilemma analogous to that faced by those hoping to define 'water' before the existence of molecular theory. In the absence of an analogous theory of the nature of living systems, interminable controversy over the definition of life is inescapable.

The concept of spontaneous generation is traced from the 17th century up to 2005, summarizing the most recent research from the history of biology.  The concept of spontaneous generation was always debated in a context where its theological implications mattered, notwithstanding denial of this by scientists such as Pasteur.

For many astronomers, the progressive development of life has been seen as a natural occurrence given proper environmental conditions on a planet: even though such beings would not be identical to humans, there would be significant parallels. A striking contrast is seen in writings of nonphysical scientists, who have held more widely differing views. But within this diversity, reasons for differences become more apparent when we see how views about extraterrestrials can be related to the differential emphasis placed on modern evolutionary theory by scientists of various disciplines. One clue to understanding the differences between the biologists, paleontologists, and anthropologists who speculated on extraterrestrials is suggested by noting who wrote on the subject. Given the relatively small number of commentators on the topic, it seems more than coincidental that four of the major contributors to the evolutionary synthesis in the 1930s and 1940s are among them. Upon closer examination it is evident that the exobiological arguments of Theodosius Dobzhansky and George Gaylord Simpson and, less directly, of H. J. Muller and Ernst Mayr are all related to their earlier work in formulating synthetic evolution. By examining the variety of views held by nonphysical scientists, we can see that there were significant disagreements between them about evolution into the 1960s. By the mid-1980s, many believed that “higher” life, particularly intelligent life, probably occurs quite infrequently in the universe; nevertheless, some held out the possibility that convergence of intelligence could occur across worlds. Regardless of the final conclusions these scientists reached about the likely prevalence of extraterrestrial intelligence, the use of evolutionary arguments to support their positions became increasingly common.

Previous space research conducted during short-term flight experiments and long-term environmental monitoring on board orbiting space stations suggests that the relationship between humans and microbes is altered in the crewed habitat in space. Both human physiology and microbial communities adapt to spaceflight. Microbial monitoring is critical to crew safety in long-duration space habitation and the sustained operation of life support systems on space transit vehicles, space stations, and surface habitats. To address this critical need, space agencies including NASA (National Aeronautics and Space Administration), ESA (European Space Agency), and JAXA (Japan Aerospace Exploration Agency) are working together to develop and implement specific measures to monitor, control, and counteract biological contamination in closed-environment systems. In this review, the current status of microbial monitoring conducted in the International Space Station (ISS) as well as the results of recent...

https://www.urbanomic.com/book/collapse-5/

One of the most fertile collaborations in contemporary popular science writing began with a biologist and a mathematician meeting for lunch at a Coventry pub in 1990. Combining their prodigious knowledge of contemporary science, the unique partnership between Jack Cohen and Ian Stewart has spawned a series of popular science books remarkable in their scope, epistemological subtlety and conceptual innovativeness. To read ‘Jack&Ian’ is to embark upon an exhilarating and intellectually enriching ride through the thickets of contemporary scientific thinking and emerge with a profound sense of how it all interconnects. Their combined critical perspective brings much-needed clarity to popular science memes such as 'emergence’, ‘chaos’ and ‘complex systems’, and they can be relied upon never to neglect the ‘big picture’. In this interview, Cohen and Stewart recount the history of their ‘complicit’ collaboration, discuss the significance of the novel ideas proposed in their co-authored works, explain their criticisms of reductionism, anthropic reasoning and astrobiology, and tell us about the aliens who helped them to write their books.

Monotheistic faiths have been routinely lambasted as incompatible with the Copernican worldview on account of being hopelessly geocentric and innocent of the true implications of a vastly expanding universe. Christological absolutism, succinctly relayed in the classical formula of Chalcedon, receives the full brunt of the criticism in view of its exclusivist soteriology, which appears to limit divine focus and grace to the human race only, as a result of the doctrine of Incarnation. For all the immense, intricate challenges of exobiology to Christianity, the present paper shall attempt to lay the groundwork for an alternative theological proposal compatible with cosmic pluralism yet faithful to the fundamentals of Trinitarian doctrine.

Absorption spectra of translucent interstellar clouds contain many known molecular bands of CN, CH+, CH, OH, OH(+), NH, C2 and C3. Moreover, one can observe more than 400 unidentified absorption features, known as diffuse interstellar bands (DIBs), commonly believed to be carried by complex, carbon-bearing molecules. DIBs have been observed in extragalactic sources as well. High S/N spectra allow to determine precisely the corresponding column densities of the identified molecules, rotational temperatures which differ significantly from object to object in cases of centrosymmetric molecular species, and even the (12)C/(13)C abundance ratio. Despite many laboratory based studies of possible DIB carriers, it has not been possible to unambiguously link these bands to specific species. An identification of DIBs would substantially contribute to our understanding of chemical processes in the diffuse interstellar medium. The presence of substructures inside DIB profiles supports the idea ...

These three propositions revolutionized humankind's concep-tion of the universe. Obviously, they were truly vast in their implica-tions. Yet they were not fully agreed to by all astronomers until the early decades of the twentieth century. There is some debate whether ...

As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of ∼106 km2 and total as much as 3–4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively young—preserving a record of the seasonal and climatic cycling of

Abstract The potential habitability of newly discovered exoplanets is initially assessed by determining whether their orbits fall within the circumstellar habitable zone of their star. However, the habitable zone (HZ) is not static in time or space, and its boundaries migrate outward at a rate proportional to the increase in luminosity of a star undergoing stellar evolution, possibly including or excluding planets over the course of the star's main sequence lifetime. We describe the time that a planet spends within the HZ as its "habitable zone lifetime." The HZ lifetime of a planet has strong astrobiological implications and is especially important when considering the evolution of complex life, which is likely to require a longer residence time within the HZ. Here, we present results from a simple model built to investigate the evolution of the "classic" HZ over time, while also providing estimates for the evolution of stellar luminosity over time in order ...

The Modern Synthesis explains the evolution of life at a mesolevel by identifying phenotype–environmental interactions as the locus of evolution and by identifying natural selection as the means by which evolution occurs. Both micro- and macroevolutionary schools of thought are post-synthetic attempts to evolutionize phenomena above and below organisms that have traditionally been conceived as non-living. Microevolutionary thought associates with the study of how genetic selection explains higher-order phenomena such as speciation and extinction, while macroevolutionary research fields understand species and higher taxa as biological individuals and they attribute evolutionary causation to biotic and abiotic factors that transcend genetic selection. The microreductionist and macroholistic research schools are characterized as two distinct epistemic cultures where the former favor mechanical explanations, while the latter favor historical explanations of the evolutionary process by identifying recurring patterns and trends in the evolution of life. I demonstrate that both cultures endorse radically different notions on time and explain how both perspectives can be unified by endorsing epistemic pluralism.

Organism-substrate interactions and their products – biogenic structures – are important biosignatures on Earth. This study discusses the application of ichnology – the study of organism-substrate interactions – to the search for present and past life beyond Earth. Three main questions are addressed: (1) Why to look for biogenic structures (i.e. traces and ichnofabrics) beyond Earth? (2) What biogenic structures to expect on other planets, moons and asteroids? (3) How to study extraterrestrial biogenic structures? Review of terrestrial evidence highlights a set of properties that make traces and ichnofabrics important for the search of potential extraterrestrial life: trace fossils preserve the activity of soft-bodied organisms; biogenic structures are resilient to processes that obliterate other biosignatures (i.e. mechanical and chemical degradation , diagenesis, tectonism and metamorphism); traces are very visible biosignatures; traces indicate environment and behaviour; traces can be universal biosignatures, i.e., biosignatures ideally suited for detecting any type of life. A model of organism-substrate interactions beyond Earth is here proposed. Expected extraterrestrial traces are those that manifest behaviours that allow to maintain homeostasis: excavations, meandering traces and biodeposition structures. Most of the existing rovers and orbiters provide basic instruments for searching these traces. It is here suggested that the search for extraterrestrial biogenic structures by rovers would also benefit from artificial adjustable lighting, GPR, LiDAR, and drilling equipment with optical televiewer. In this study, open-access databases of rover and orbiter imagery have been searched for traces and ichno-fabrics, but no unquestionable evidence of biogenic structures beyond Earth has been found besides those produced by humans. This sounds along the lines of the famous Fermi Paradox: if the universe is teeming with aliens, where are their traces? Results of this search show that habitable environments are not the only place to look for biogenic structures; non-habitable environments such as moons without atmosphere can favour the preservation of shallow-tier traces. The better preservation potential of traces compared to other biosignatures greatly widens the issue of planetary protection, including the interaction between astronauts or vehicles and the substrate may produce disturbances. Although this study highlights a new direction of study with the tools and concepts of ichnology, dialogue MARK between the astrobiological and ichnological communities is needed to use its full potential and possibly answer one of the major questions of science: Does life exist beyond Earth?

It has been widely acknowledged that self-replicating space-probes (SRPs) could explore the galaxy very quickly relative to the age of the galaxy. An obvious implication is that SRPs produced by extraterrestrial civilizations should have arrived in our solar system millions of years ago, and furthermore, that new probes from an ever-arising supply of civilizations ought to be arriving on a constant basis. The lack of observations of such probes underlies a frequently cited variation of the Fermi Paradox. We believe that a predilection for ETI-optimistic theories has deterred consideration of incompatible theories. Notably, SRPs have virtually disappeared from the literature. In this paper, we consider the most common arguments against SRPs and find those arguments lacking. By extension, we find recent models of galactic exploration which explicitly exclude SRPs to be unfairly handicapped and unlikely to represent natural scenarios.
We also consider several other models that seek to explain the Fermi Paradox, most notably percolation theory and two societal- collapse theories. In the former case, we find that it imposes unnatural assumptions which likely render it unrealistic. In the latter case, we present a new theory of interstellar transportation bandwidth which calls into question the validity of societal-collapse theories.
Finally, we offer our thoughts on how to design future SETI programs which take the conclusions of this paper into account to maximize the chance of detection.

O artigo procura avaliar criticamente, à luz do conhecimento científico actual e daquilo que parece razoável especular filosoficamente a partir dele, se haverá mais e melhores razões para a humanidade tentar evitar ou procurar activamente um possível contacto com uma eventual civilização extratrrestre.

Lo scrittore Peter Kolosimo (1922-1984) ha contribuito alla diffusione e discussione di numerosi temi attinenti al misterioso, all’insolito e al paranormale. Tra questi si annoverano l’interazione tra extraterrestri ed esseri umani in tempi remoti, e l’esistenza, sempre in epoche lontanissime, di Atlantide e Mu, continenti distrutti da immani catastrofi dopo che le loro civiltà avevano raggiunto uno sviluppo tecnologico avanzato.

La bibliografia kolosimiana è molto ricca, contando diciassette libri tradotti in (almeno) dodici lingue, e una miriade di articoli, tra cui quelli apparsi su Pi Kappa, mensile dalla vita breve ma intensa (novembre 1972 - ottobre 1973), che fu fondato e diretto dallo stesso Kolosimo. I suoi scritti non vertono solo su argomenti misteriosi e controversi; Kolosimo si è dedicato anche alla divulgazione scientifica (particolarmente cara gli era la storia dell’esplorazione spaziale), alla psicoanalisi, all’educazione sessuale e alla narrativa, sia fantascientifica, sia umoristica.

Avvicinandosi il centenario della nascita dello scrittore (il cui vero nome era Pier Domenico Colosimo), ho sentito il desiderio di conoscerlo meglio. Se è vero che nel tempo molti autori hanno seguito le orme di Kolosimo (e alcuni lo avevano preceduto sugli stessi sentieri), è altrettanto vero che il suo stile e la sua visione del mondo hanno caratteristiche uniche, e meritano un’attenzione speciale. A questo si aggiunge che l’affascinante biografia di Kolosimo presenta ancora alcuni misteri.

Essenziale, per capire Kolosimo “com’era davvero”, è stata la conversazione con Caterina Kolosimo, che come moglie, collaboratrice e co-autrice è stata al fianco di Peter per più di vent’anni.

To the Voyager spacecraft, Enceladus seemed like a fresh, smooth snowball.

It was Cassini that first noticed how remarkable this small Saturn moon is indeed whose fissures blow fountains into the sky as if it were the Iceland of space.

Cassini has now been dumped into Saturn, but what it has observed is by no means understood. Where does the heat originate that powers the geysers of Enceladus? Where do the organic substances inside come from? Can there even be life inside?

This book presents the outstanding observations of Cassini for the first time.