A linear correlation analysis between the Mars Odyssey neutron fluxes and various surface parameters indicates that the annual maximum surface temperature is the most important factor controlling the soil water content in the surficial (upper few tens of centrimetres) layers of the Martian soil. This is likely to be associated with the higher enthalpy of hydration of minerals in comparison with the enthalpy of sublimation of ice, which is presumably almost absent in the surficial layer. While presently the maximum surface temperature occurs near 30° S because of perihelion in late southern spring, the season of perihelion periodically migrates by virtue of precession. Consequently, the maximum surface temperature as well as the driest place on Mars should move from one hemisphere to the other with a period of about 51 000 yr. A significant amount of surficial (adsorbed) water would then be exchanged between the hemispheres and between the soil and other reservoirs, especially the polar caps and the polar layered deposits, and is probably borne out by the stratigraphic structure of these deposits. It is suggested that the water migration driven by the orbital eccentricity and precession may be as important as the obliquity-driven exchange of water, particularly very close to the surface, where ground ice is unstable.

The zones of liquid water stability oscillate somewhat in a north–south direction in the course of the precession cycle, but are most prevalent in parts of the low and mid northern latitudes as well as in the Hellas Basin. The thermal stability of liquid water tends to be high where the near-surface soil water content is low, indicating that the periodic melting of ground ice by solar heating is not a likely source of liquid water on the surface, but some episodic processes should provide water, if any.

An enhanced soil water content near the surface is always accompanied with a reduced peak ultraviolet flux, both reducing the chemical reactivity of the soil. In the present epoch the northern hemisphere may represent astrobiologically more clement environmental conditions.

The Fourier transform-Raman spectra of two lacustrine sediment cores from Antarctic sites are reported. The Lake Hoare specimens were predominantly calcium carbonate, quartz and β-carotene, with chlorophyll and calcium sulphate being noted as minor components. No evidence was found for iron (III) oxide or oxy-hydroxide bands. The Lake Nella specimens, in contrast, contain chlorophyll and quartz predominantly, but the absence of β-carotene is noteworthy. Here, the presence of haematite and a haematite–goethite mixture have been identified, with weaker features such as those of scytonemin, characteristic of cyanobacterial mats. The Raman spectra indicate that two different types of lake chemistry have been operating and several reasons are proposed for this.

We undertook observations with the Green Bank Telescope, simultaneously with the 300 m telescope in Arecibo, as a follow-up of a possible flare of radio emission from Ross 128. We report here the non-detections from the GBT observations in C band (4–8 GHz), as well as non-detections in archival data at L band (1.1–1.9 GHz). We suggest that a likely scenario is that the emission comes from one or more satellites passing through the same region of the sky.

Current assessments of bioburden embedded in spacecraft materials are based on work performed in the Viking era (1970s), and the ability to culture organisms extracted from such materials. To circumvent the limitations of such approaches, DNA-based techniques were evaluated alongside established culturing techniques to determine the recovery and survival of bacterial spores encapsulated in spacecraft-qualified polymer materials. Varying concentrations of Bacillus pumilus SAFR-032 spores were completely embedded in silicone epoxy. An organic dimethylacetamide-based solvent was used to digest the epoxy and spore recovery was evaluated via gyrB-targeted qPCR, direct agar plating, most probably number analysis, and microscopy. Although full-strength solvent was shown to inhibit the germination and/or outgrowth of spores, dilution in excess of 100-fold allowed recovery with no significant decrease in cultivability. Similarly, qPCR (quantitative PCR) detection sensitivities as low as ∼103 CFU ml−1 were achieved upon removal of inhibitory substances associated with the epoxy and/or solvent. These detection and enumeration methods show promise for use in assessing the embedded bioburden of spacecraft hardware.

Sedimentary and magmatic rocks and their distinct sulphur isotopic signatures indicate the sources and processes of sulphur cycling, in particular through the analysis of all four stable sulphur isotopes (32S, 33S, 34S and 36S). Research over the past 15 years has substantially advanced our understanding of sulphur cycling on the early Earth, most notably through the discovery of mass-independently fractionated sulphur isotopic signatures. A strong atmospheric influence on the early Archean global sulphur cycle is apparent, much in contrast to the modern world. Diverse microbially driven sulphur cycling is clearly discernible, but its importance for Earth surface environments remains to be quantified.

We address a recently posed question: ‘Why Do So Many Astronomy (and Astrobiology) Discoveries Fail to Live Up to the Hype?’ We expand it to cover hype within science in general. Our answer relies on working definitions of hype and skin in the game, as applied to research science, and a game theory model for the stability of cooperative science. Low skin in the game allows internal feedbacks, within the research science community, to initiate increased hype and a drift toward structural instability. The instability leads to the deterioration of cooperative equilibria, which further enhances hype. Along the drift, the number of results hyped as breakthroughs will increase and more claims will fail to live up to the hype. This can lead to the public perception that science is moving backwards and a shift in the perception of what scientists, and science, values. Although a hype instability can be initiated by external nudges, a bigger role is played by the internal dynamics of the system, i.e. the collective of working scientists. Corrections for a drift toward instability should, likewise, focus on internal structure. Proposed external shifts on how research is disseminated will add restrictions to a system that can do more harm than good.

The colonization of Mars will require obtaining building materials which can be put in place and processed into buildings via various constructive technologies. We tried to use artificial Martian ground – AMG (GEO PAT 11-234 (2015)) and special resins for the preparation of building block prototypes. The composite material has been obtained based on the AMG as filler, epoxy resin (type ED-20) and tetraethoxysilane – TEOS. We have studied strengthening – softening temperatures and water absorption of the AMG polymer composites that are determined by epoxy resin and TEOS modification. Comparison of the experimental results shows that composites containing modified filler have higher values of the maximum ultimate strength, resistance and flexibility parameters than unmodified composites with definite loading. Modified composites also have a higher softening temperature and lower water absorption.

There is a record of the positive effects of astrobiological research for the natural sciences and eventually for their technological use on Earth. However, on the philosophical effects, this is not as visible as the other sciences, which is why it can be assumed that it is a waste of time speculating on astrobioethics or also on the philosophy of astrobiology. This is the reason why this work seeks to identify and sustain the philosophical utility of astrobioethics. To achieve this, this article focuses on three essential aspects: teloempathy, education and astrotheology. Russell's argument about the value of philosophy will be used as a fundamental basis for the usefulness of astrobioethics.

If the discoveries of C60 and C70 fullerenes in terrestrial hard rocks are real, then some of these may have formed in the solid state by dehydrogenation-driven ‘zip-up’ of C60Hn and C70Hm progenitors. At three sites of such fullerene discoveries the building blocks for these large molecules may have come from algal remains.

This paper is profoundly innovative for the Evo-SETI (Evolution and SETI) mathematical theory. While this author's previous papers were all based on the notion of a b-lognormal, that is a probability density function in the time describing one's life between birth and ‘senility’ (the descending inflexion point), in this paper the b-lognormals range between birth and peak only, while a descending parabola covers the lifespan after the peak and down to death. The resulting finite curve in time is called a LOGPAR, a nickname for ‘b-LOGnormal and PARabola’. The advantage of such a formulation is that three variables only (birth, peak and death) are sufficient to describe the whole Evo-SETI theory and the senility is discarded forever and so is the normalization condition of b-lognormals: only the shape of the b-lognormals is kept between birth and peak, but not its normalization condition.

In addition, further advantages exist:

1) The notion of ENERGY becomes part of Evo-SETI theory. This is in addition to the notion of ENTROPY already contained in the theory as the Shannon Information Entropy of b-lognormals, as it was explored in this author's previous papers. Actually, the LOGPAR may now be regarded as a POWER CURVE, i.e. a curve expressing the power of the living being to which it refers. And this power is to be understood both in the strict sense of physics (i.e. a curve measured in Watts) and in the loose sense of ‘political power’ if the logpar refers to a Civilization.

Then the integral in the time of this power curve is, of course, the ENERGY either absorbed or produced by the physical phenomenon that the LOGPAR is describing in the time. For instance, if the logpar shows the time evolution of the Sun over about 10 billion years, the integral of such a curve is the energy produced by the Sun over the whole of its lifetime. Or, if the logpar describes the life of a man, the integral is the energy that this man must use in order to live.

2) The PRINCIPLE OF LEAST ENERGY, reminiscent of the Principle of Least Action, i.e. the key stone to all Physics, also enters now into the Evo-SETI Theory by virtue of the so-called LOGPAR HISTORY FORMULAE, expressing the b-lognormal's mu and sigma directly in terms of the three only inputs b, p, d. The optimization of the lifetime of a living creature, or of a Civilization, or of a star, is obtained by setting to zero the first derivative of the area under the logpar power curve with respect to sigma. That yields the best value of both mu and sigma fulfilling the Principle of Least Energy for Evo-SETI Theory.

3) We also derive for the first time a few more mathematical equations related to the ‘adolescence’ (or ‘puberty’) time, i.e. the time when the living organism acquires the capability of producing offsprings. This time is defined as the abscissa of ascending inflection point of the b-lognormal between birth and peak. In addition, we prove that the straight line parallel to the time axis and departing from the puberty time comes to mean the ‘Fertility Span’ in between puberty and the EOF (End-Of-Fertility time), which is where the above straight line intersects the descending parabola. All these new results apply well to the description of Man as the living creature to which our Evo-SETI mathematical theory perfectly applies.

In conclusion, this paper really breaks new mathematical ground in Evo-SETI Theory, thus paving the way to further applications of the theory to Astrobiology and SETI.

The detection of atmospheric methane on Mars implies an active methane source. This introduces the possibility of a biotic source with the implied need to determine whether the methane is indeed biotic in nature or geologically generated. There is a clear need for robotic algorithms which are capable of manoeuvring a rover through a methane plume on Mars to locate its source. We explore aspects of Mars methane plume modelling to reveal complex dynamics characterized by advection and diffusion. A statistical analysis of the plume model has been performed and compared to analyses of terrestrial plume models. Finally, we consider a robotic search strategy to find a methane plume source. We find that gradient-based techniques are ineffective, but that more sophisticated model-based search strategies are unlikely to be available in near-term rover missions.

From the numerous detected planets outside the Solar System, no terrestrial planet comparable with our Earth has been discovered so far. The search for an Exo-Earth is certainly a big challenge which may require the detections of planetary systems resembling our Solar System in order to find life like on Earth. However, even if we find Solar System analogues, it is not certain that a planet in Earth position will have similar circumstances as those of the Earth. Small changes in the architecture of the giant planets can lead to orbital perturbations which may change the conditions of habitability for a terrestrial planet in the habitable zone (HZ). We present a numerical investigation where we first study the motion of test-planets in a particular Jupiter–Saturn configuration for which we can expect strong gravitational perturbations on the motion at the Earth's position according to a previous work. In this study, we show that these strong perturbations can be reduced significantly by the neighbouring planets of Earth. In the second part of our study, we investigate the motion of test-planets in inclined Jupiter–Saturn systems where we analyse changes in the dynamical behaviour of the inner planetary system. Moderate values of inclination seem to counteract the perturbations in the HZ, while high inclinations induce more chaos in this region. Finally, we carry out a stability study of the actual orbits of Venus, Earth and Mars moving in the inclined Jupiter–Saturn systems for which we used the Solar System parameters. This study shows that the three terrestrial planets will only move in low-eccentric orbits if Saturn's inclination is ≤10°. Therefore, it seems that it is advantageous for the habitability of Earth when all planets move nearly in the same plane.

How photosynthesis by Precambrian cyanobacteria oxygenated Earth's biosphere remains incompletely understood. Here it is argued that the oxic transition, which took place between approximately 2.3 and 0.5 Gyr ago, required a great proliferation of cyanobacteria, and this in turn depended on their ability to fix nitrogen via the nitrogenase enzyme system. However, the ability to fix nitrogen was not a panacea, and the rate of biospheric oxygenation may still have been affected by nitrogen constraints on cyanobacterial expansion. Evidence is presented for why cyanobacteria probably have a greater need for fixed nitrogen than other prokaryotes, underscoring the importance of their ability to fix nitrogen. The connection between nitrogen fixation and the evolution of photosynthesis is demonstrated by the similarities between nitrogenase and enzymes critical for the biosynthesis of (bacterio)chlorophyll. It is hypothesized that biospheric oxygenation would not have occurred if the emergence of cyanobacteria had not been preceded by the evolution of nitrogen fixation, and if these organisms had not also acquired the ability to fix nitrogen at the beginning of or very early in their history. The evolution of nitrogen fixation also appears to have been a precondition for the evolution of (bacterio)chlorophyll-based photosynthesis. Given that some form of chlorophyll is obligatory for true photosynthesis, and its light absorption and chemical properties make it a ‘universal pigment’, it may be predicted that the evolution of nitrogen fixation and photosynthesis are also closely linked on other Earth-like planets.

Assuming that securing the long-term survival of humans and Earth life is a valid goal, we briefly compare the strategies of building standard space colonies, such as on Mars, and embryo space colonization (ESC). In ESC embryos of humans and other Earth species would be sent to exoplanets and raised there via ectogenesis and android assistants. We find that the potential for securing long-term survival is far greater for ESC than for standard colonies, while the bioethical and other risks are far fewer.

The concept of exoplanetary habitability is evolving. The driving force is a desire to define the biological potential of planets and identify which can host complex and possibly intelligent life. To assess this in a meaningful manner, climate models need to be applied to realistic surfaces. However, the vast majority of climate models are developed using generic aquaplanet, or swamp planet, scenarios that provide uniform, surface frictional coefficients. However, aside from planets with largely uniform oceans, these models are not obviously useful when it comes to understanding the impact of climate on biodiversity. Here, we show that contrary to expectation, the aquaplanet models can be directly applied to planets with a variety of land areas, with little need for modification. Using this premise, this paper provides a simple mathematical framework that may be applied to more complex planetary surfaces and identifies the majority of the climate-model components that are needed to accurately determine the biological potential of habitable exoplanets. As a proof-of-concept, an available climate model for Proxima b is used to determine its biological potential, given a suitable atmosphere.

Astrotheology is presented as a discipline of study that manages to complement theology and science. It considers that each one has its own role and that as long as there is no reductionism that wants to monopolize the place of the other, fluid communication between both is possible. Therefore, it is worth examining epistemologically astrotheology in the light of astrobiology. To achieve this, we will highlight the aspect of experience in order to relate it to transdisciplinarity.

Nuclear astrophysics is a relatively young science; it is about half a century old. It is a multidisciplinary subject, since it combines nuclear physics with astrophysics and observations in astronomy. It also addresses fundamental issues in astrobiology through the formation of elements, in particular those required for a carbon-based life. In this paper, a rapid overview of nucleosynthesis is given, mainly from the point of view of nuclear physics. A short historical introduction is followed by the definition of the relevant nuclear parameters, such as nuclear reaction cross sections, astrophysical S-factors, the energy range defined by the Gamow peak and reaction rates. The different astrophysical scenarios that are the sites of nucleosynthesis, and different processes, cycles and chains that are responsible for the building of complex nuclei from the elementary hydrogen nuclei are then briefly described.

In the light of current scientific assessments of human-induced climate change, we investigate an experimental model to inform how resource-use strategies may influence interplanetary and interstellar colonization by intelligent civilizations. In doing so, we seek to provide an additional aspect for refining the famed Fermi Paradox. The model described is necessarily simplistic, and the intent is to simply obtain some general insights to inform and inspire additional models. We model the relationship between an intelligent civilization and its host planet as symbiotic, where the relationship between the symbiont and the host species (the civilization and the planet's ecology, respectively) determines the fitness and ultimate survival of both organisms. We perform a series of Monte Carlo Realization simulations, where civilizations pursue a variety of different relationships/strategies with their host planet, from mutualism to parasitism, and can consequently ‘infect’ other planets/hosts. We find that parasitic civilizations are generally less effective at survival than mutualist civilizations, provided that interstellar colonization is inefficient (the maximum velocity of colonization/infection is low). However, as the colonization velocity is increased, the strategy of parasitism becomes more successful, until they dominate the ‘population’. This is in accordance with predictions based on island biogeography and r/K selection theory. While heavily assumption dependent, we contend that this provides a fertile approach for further application of insights from theoretical ecology for extraterrestrial colonization – while also potentially offering insights for understanding the human–Earth relationship and the potential for extraterrestrial human colonization.

In this paper we consider a scenario in which Carl Sagan's Copernican principle is more likely than its negation. Thus, assuming that the existence of an extraterrestrial intelligence (ETI) is reasonably likely, the paper considers the possibility of an ETI that is unable to recognize humans as intelligent beings. The paper presents the rationale for such an assumption. It also discusses the possible consequences for humanity of such a scenario. In this paper, we argue why the scenario under discussion is actually more positive for humanity than a scenario in which ETI would be capable of recognizing humanity as an intelligent species. We also point to feminist approaches to SETI issues exposing the role played by the specific evolutionary and developmental context of potential ETI.

Dendrochronological research was carried out on 23 trees samples (Larix sibirica and Picea obovata) sampled during the 1999 expedition in two locations, close to the epicentre zone and near Cheko lake (N 60°57′, E 101°51′). Basal Area Increment (BAI) analysis has shown a general long growth suppression before 1908, the year of Tunguska event (TE), followed by a sudden growth increase due to diminished competition of trees that died due to the event. In one group of the trees, we detected growth decrease for several years (due to damage to the trunk, branches and crown), followed by growth increase during the following 4–14 years. We show that trees that germinated after the TE, and living in close proximity of Cheko lake (Cheko lake trees) had different behaviour patterns when compared to those trees living further from Cheko lake, inside the forest (Forest trees). Cheko lake trees have shown a vigorous continuous growth increase. Forest trees have shown a vigorous growth during the first 10–30 years of age, followed by a period of suppressed growth. We interpret the suppressed growth by the re-established competition with the surroundings trees. Cheko lake pattern, however, is consistent with the formation of the lake at the time of TE. This observation supports the hypothesis that Cheko lake formation is due to a fragment originating during TE, creating a small impact crater into the permafrost and soft alluvial deposits of Kimku River plain. This is further supported by the fact that Cheko lake has an elliptical shape elongated towards the epicentre of TE.