With the aim to visualize the span of time since the formation of our Universe we have set up a nature and hiking trail called ‘Time Trek’. The 13.7 km length of the trail corresponds to the age of the Universe, and portrays its history including events important for Earth and life. One kilometre corresponds to a billion years, and one metre to a million years of time. The trek combines astronomical, physical, geological and biological time lines, and presents a holistic view of the history of time. It helps people to comprehend the causal and temporal connections of different phenomena. To the trekker, it offers a concrete experience of the lengths and proportions of different time periods, which otherwise are very difficult to understand.

Although astrobiology is a science midway between the life and physical sciences, it has surprisingly remained largely disconnected from recent trends in certain branches of both life and physical sciences. We discuss potential applications to astrobiology of approaches that aim at integrating rather than reducing. Aiming at discovering how systems properties emerge has proved valuable in chemistry and in biology. The systems approach should also yield insights into astrobiology, especially concerning the ongoing search for alternative abodes for life. This is feasible since new data banks in the case of astrobiology – considered as a branch of biology – are of a geophysical/astronomical kind, rather than the molecular biology data that are used for questions related firstly, to genetics in a systems context and secondly, to biochemistry for solving fundamental problems, such as protein or proteome folding. By focusing on how systems properties emerge in astrobiology we consider the question: can life in the universe be interpreted as an emergent phenomenon? In the search for potential habitable worlds in our galactic sector with current space missions, extensive data banks of geophysical parameters of exoplanets are rapidly emerging. We suggest that it is timely to consider life in the universe as an emergent phenomenon that can be approached with methods beyond the science of chemical evolution – the backbone of previous research in questions related to the origin of life. The application of systems biology to incorporate the emergence of life in the universe is illustrated with a diagram for the familiar case of our own planetary system, where three Earth-like planets are within the habitable zone (HZ) of a G2 V (the complete terminology for the Sun in the Morgan–Keenan system) star. We underline the advantage of plotting the age of Earth-like planets against large atmospheric fraction of a biogenic gas, whenever such anomalous atmospheres are discovered in these worlds. A prediction is made as to the nature of the atmospheres of the planets that lie in the stellar HZs.

We consider the suggestion that, as a matter of caution, the deliberate broadcast of signals to the cosmos should be proscribed. We explore the likely capabilities of extraterrestrial societies that might conceivably pose a threat to our species and show that this suggestion is without merit because even if followed, it would fail to keep our existence secret. In addition, trying to limit signalling activities would be a burden on our descendants, crippling their own activities for the indefinite future. A corollary to these considerations affects the search for extraterrestrial intelligence (SETI): namely, it seems inarguable that technologically advanced beings will assume that other societies are capable of detecting their leakage. Consequently, the premise that SETI should expect to find deliberate beacons from other worlds may be mistaken.

The paper considers the two-century-old problem of how solar spots influence biological objects on the Earth. It describes the modern state of the kT-problem, which for a long time has been the most difficult obstacle in explaining solar activity effects. Based on recent advances in spin chemistry and magnetoplasticity physics, it is shown that a ‘molecular target’ sensitive to weak electromagnetic fields is spins in non-equilibrial states of the molecular system. A way of how solar spots can influence Earth's molecular, including biological, processes through a ‘transparency window’ in the Earth's atmosphere is proposed.

Gale crater formed from an impact on Mars ∼3.6 billion years ago. It hosts a central mound nearly 100 km wide and ∼5 km high, consisting of layered rocks with a variety of textures and spectral properties. The oldest exposed layers contain variably hydrated sulphates and smectite clay minerals, implying an aqueous origin, whereas the younger layers higher on the mound are covered by a mantle of dust. Fluvial channels carved into the crater walls and the lower mound indicate that surface liquids were present during and after deposition of the mound material. Numerous hypotheses have been advocated for the origin of some or all minerals and layers in the mound, ranging from deep lakes to playas to mostly dry dune fields to airfall dust or ash subjected to only minor alteration driven by snowmelt. The complexity of the mound suggests that multiple depositional and diagenetic processes are represented in the materials exposed today. Beginning in August 2012, the Mars Science Laboratory rover Curiosity will explore Gale crater by ascending the mound's northwestern flank, providing unprecedented new detail on the evolution of environmental conditions and habitability over many millions of years during which the mound strata accumulated.

There have been a number of hypotheses regarding abiogenesis, the ‘Metabolism First’ model and the ‘RNA World Hypothesis’ are two such examples. All theories on abiogenesis make a set of unstated assumptions with regard to the elemental make up of life or only apply the theory to a primitive earth model. This paper reviews current knowledge from the myriad of observations from a variety of scientific disciplines and applies generally understood thermodynamic reasoning to explain the formation of molecules known to be used by life. These arguments are used in this paper to construct a set of new hypotheses which govern universal abiogenesis. The intention of this paper is to show by the application of our known laws of science that life is the end sequence of events of the fundamental forces which affect the entire universe. From these events a new hypotheses on abiogenesis can be formulated. The hypotheses proposed by this paper are incorporated in many of the current theories of abiogenesis, either assumed or accepted but very rarely stated or explained. The proposed set of five hypotheses are: (1) any celestial mass that has a body of liquid water and therefore has access to energy will form at least the building blocks of life, if not life itself. (2) The major component of any life form anywhere in the universe will be H2O. (3) Any organism, anywhere in the universe, will be carbon-based. (4) All life in the universe will be composed of nucleic acid based molecules as its code for life. (5) The cell is the universal unit of life. Throughout this paper the background to the formulation of these hypotheses is discussed, as is the explanation of why these hypotheses are universal and not limited to an application of a primitive earth model. This set of hypotheses is also testable as any investigation of a celestial body which contains liquid water (e.g. Europa) will quickly provide evidence to prove or refute the proposed theory.

A model of the spatial emergence of an interstellar civilization into a uniform distribution of habitable systems is presented. The process of emigration is modelled as a three-dimensional probabilistic cellular automaton. An algorithm is presented which defines both the daughter colonies of the original seed vertex and all subsequent connected vertices, and the probability of a connection between any two vertices. The automaton is analysed over a wide set of parameters for iterations that represent up to 250 000 years within the model's assumptions. Emigration patterns are characterized and used to evaluate two hypotheses that aim to explain the Fermi Paradox. The first hypothesis states that interstellar emigration takes too long for any civilization to have yet come within a detectable distance, and the second states that large volumes of habitable space may be left uninhabited by an interstellar civilization and Earth is located in one of these voids.

The search for extra-terrestrial intelligence (SETI) has been performed principally as a one-way survey, listening of radio frequencies across the Milky Way and other galaxies. However, scientists have engaged in an active messaging only rarely. This suggests the simple rationale that if other civilizations exist and take a similar approach to ours, namely listening but not broadcasting, the result is a silent universe. A simple game theoretical model, the prisoner's dilemma, explains this situation: each player (civilization) can passively search (defect), or actively search and broadcast (cooperate). In order to maximize the payoff (or, equivalently, minimize the risks) the best strategy is not to broadcast. In fact, the active search has been opposed on the basis that it might be dangerous to expose ourselves. However, most of these ideas have not been based on objective arguments, and ignore accounting of the possible gains and losses. Thus, the question stands: should we perform an active search? I develop a game-theoretical framework where civilizations can be of different types, and explicitly apply it to a situation where societies are either interested in establishing a two-way communication or belligerent and in urge to exploit ours. The framework gives a quantitative solution (a mixed-strategy), which is how frequent we should perform the active SETI. This frequency is roughly proportional to the inverse of the risk, and can be extremely small. However, given the immense amount of stars being scanned, it supports active SETI. The model is compared with simulations, and the possible actions are evaluated through the San Marino scale, measuring the risks of messaging.

This paper proposes a long-term scheme for robotic exploration of the galaxy, and then considers the implications in terms of the ‘Fermi paradox’ and our search for extraterrestrial intelligence (ETI). We discuss the ‘Galactic ecology’ of civilizations in terms of the parameters T (time between ET civilizations arising) and L, the lifetime of these civilizations. Six different regions are described.

How prebiotic metabolic pathways could have formed is an essential question for the origins of life on early Earth. From the abiogenetic point of view, the emergence of primordial metabolism may be postulated as a continuum from Earth's geochemical processes to chemoautotrophic biochemical procedures on mineral surfaces. In the present study, we examined in detail the reversible amination of α-ketoglutarate on UV-irradiated ZnS particles under variable reaction conditions such as pH, temperature, hole scavenger species and concentrations, and different amino acids. It was observed that the reductive amination of α-ketoglutarate and the oxidative amination of glutamate were both effectively performed on ZnS surfaces in the presence and absence of a hole scavenger, respectively. Accordingly, a photocatalytic mechanism was proposed. The reversible photochemical reaction was more efficient under basic conditions but independent of temperature in the range of 30–60 °C. SO32− was more effective than S2− as the hole scavenger. Finally, we extended the glutamate dehydrogenase-like chemistry to a set of other α-amino acids and their corresponding α-oxo acids and found that hydrophobic amino acid side chains were more conducive to the reversible redox reactions. Since the experimental conditions are believed to have been prevalent in shallow water hydrothermal vent systems of early Earth, the results of this work not only suggest that the ZnS-assisted photochemical reaction can regulate the redox equilibrium between α-amino acids and α-oxo acids, but also provide a model of how prebiotic metabolic homoeostasis could have been developed and regulated. These findings can advance our understanding of the establishment of archaic non-enzymatic metabolic systems and the origins of autotrophy.

The adsorption of organic molecules on mineral matrices might have played a fundamental role in processes that led to the emergence of life. We investigated the adsorption properties of the nucleobases adenine, cytosine, uracil and hypoxanthine on magnesium oxide (MgO), determining the single solute batch equilibrium adsorption isotherms. Langmuir-type isotherms were fitted to data, assuming a rapid reversible equilibration of adsorption, demonstrated effectively through desorption experiments. The Langmuir equilibrium adsorption constant K and the amount of the solute per unit of adsorbent mass necessary to complete the monolayer b were calculated. The results indicate that MgO is a good adsorbent for nucleobases (adenine > uracil > hypoxantine > cytosine), suggesting a role of metal oxides in concentrating biomolecules in prebiotic conditions that might have favoured the passage from geochemistry to biochemistry.

We live in the epoch of explosive development of astrobiology, a novel interdisciplinary field dealing with the origin, evolution and the future of life. The relationship between cosmology and astrobiology is much deeper than it is usually assumed – besides a similarity in the historical model of development of these two disciplines, there is an increasing number of crossover problems and thematic areas which stem from considerations of Copernicanism and observation selection effects. Such a crossover area is both visualized and heuristically strengthened by introduction of the astrobiological landscape, describing complexity of life in the most general context. We argue that this abstract landscape-like structure in the space of astrobiological parameters is a concept capable of unifying different strands of thought and research, a working concept and not only a metaphor. By analogy with phase spaces of complex physical systems, we can understand the astrobiological landscape as a set of viable evolutionary histories of life in a particular region of space. It is a notion complementary to the classical concept of biological morphological space, underscoring the fact that modern astrobiology offers a prospect of both foundational support and vast extension of the domain of applicability of the Darwinian biological evolution. Such a perspective would strengthen foundations upon which various numerical models can be built; the lack of such quantitative models has often been cited as the chief weakness of the entire astrobiological enterprise.

It has been argued that the limited set of proteins used by life as we know could not have arisen by the process of Darwinian selection from all possible proteins. This probabilistic argument has a number of implicit assumptions that may not be warranted. A variety of considerations are presented to show that the number of amino acid sequences that need to have been sampled during the evolution of proteins is far smaller than assumed by the argument.