In this paper we exemplify a biased synthesis that can be relevant in primitive scenarios. We perform experiments simulating a possible prebiotic environment, in which an organic compound is adsorbed in soil and exposed to an energy source. To this end, carboxylic acids were adsorbed in a clay mineral and the systems were exposed to radiation. We observed that radiation decomposition in solution changes drastically if the system contains a clay mineral. Both solid surfaces and radiation play an important role.

The in situ detection of organic molecules in space is key to understanding the variety and the distribution of the building blocks of life, and possibly the detection of extraterrestrial life itself. Gas chromatography mass spectrometry (GC-MS) has been the most sensitive analytical strategy for organic analyses in flight, and was used on missions from NASA's Viking, Phoenix, Curiosity missions to ESA's Rosetta space probe. While pyrolysis GC-MS revealed the first organics on Mars, this step alters or degrades certain fragile molecules that are excellent biosignatures including polypeptides, oligonucleotides and polysaccharides, rendering the intact precursors undetectable. We have identified a solution tailored to the detection of biopolymers and other biomarkers by the use of liquid-based capillary electrophoresis and electrochromatography. In this study, we show that a capillary electrochromatography approach using monolithic stationary phases with tailor-made surface chemistry can separate and identify various polycyclic aromatic hydrocarbons, nucleobases and aromatic acids that could be formed under astrophysically relevant conditions. In order to simulate flyby organic sample capture, we conducted hypervelocity impact experiments which consisted of accelerating peptide-soaked montmorillonite particles to a speed of 5.6 km s−1, and capturing them in an amorphous silica aerogel of 10 mg cm−3 bulk density. Bulk peptide extraction from aerogel followed by capillary zone electrophoresis led to the detection of only two stereoisomeric peptide peaks. The recovery rates of each step of the extraction procedure after the hypervelocity impact suggest that major peptide loss occurred during the impact. Our study provides initial exploration of feasibility of this approach for capturing intact peptides, and subsequently detecting candidate biomolecules during flight missions that would be missed by GC-MS alone. As the monolith-based electrochromatography technology could be customized to detect specific classes of compounds as well as miniaturized, these results demonstrate the potential of the instrumentation for future astrobiology-related spaceflight missions.

The Fermi Paradox (or Question) has moved back into central focus. This is for a number of reasons, not least the evidence for both the abundance and antiquity of many extra-solar systems, the extrapolation of current technological trends to suggest that even inter-galactic colonization (by self-replicating machines) is plausible (if not desirable), and the recurrence of evolutionary solutions (convergence) in the terrestrial biosphere suggesting that features such as intelligence and tool-making are not fortuitous outcomes, but frequent if not universal. Here I review the three possible solutions to the Fermi Paradox. First, extraterrestrials certainly exist (and may be abundant), but for one reason or another (probably mundane) we have not yet met them, or at least found evidence for their existence. Second, against all expectations, we are alone. Third, we have entirely misunderstood the sort of universe we live in and have become unwitting hostages to a strict materialist explanandum that in refusing to acknowledge the other realities of our Universe has derailed any prospect of explaining the apparent absence of extraterrestrials.

In this paper, we connect ideas of the astrobiological and ecological schools to quantify habitability. We show how habitability indexes, devised using the astrobiologically inspired Quantitative Habitability Theory (QHT), can be embedded into ecological models of trophic levels. In particular, we address the problem of spatial-temporal scales. It turns out that the versatility of QHT allows to treat spatial and temporal scales typical of ecological studies. As a habitability index, we propose a new version of our Aquatic Primary Habitability, devised by some of us and formerly applied to saltwater ecosystems (both ocean and coastal) and now applied to freshwater. Although the aim of the paper is to outline the methodology rather than realism, initial steps for parameterization are considered for lakes of South-Central Chile.

The habitable zone is the circumstellar region in which a terrestrial-mass planet with an atmosphere can sustain liquid water on its surface. However, despite the usefulness of this concept, it is being found to be increasingly limited in a number of ways. The following is known: (i) Liquid water can exist on worlds for reasons unrelated to its specific distance from a star. (ii) Energy sources can exist for reasons unrelated to the distance to a star. Furthermore, the habitable zone is based on both astronomy – the distance and stellar energy – and chemistry – liquid water and the right temperature. However, these factors are only part of the consideration. Thus, discussions of habitability and the possibility for the emergence of life on a world must consider the evolutionary principles that govern life as well as the laws that govern stellar and planetary science. This is important because the following is also known: (iii) The temporal window for the emergence of life is within 600 million years. (iv) The Earth was an extreme environment overall in the period when this window existed. (v) The first life was necessarily fragile. Therefore, chemical evolution must have taken place in a relatively protected and restricted environment. Thus, rather than as in the Goldilocks zone, which focuses too narrowly on the world as a whole, this paper suggests that it is better to focus on a particular region and time period on a world, in which conditions fit for habitability exist. Thus, the following is suggested: ‘The Goldilocks Edge is a spatial and temporal window on an astronomical body or planemo, where liquid solvents, SPONCH elements and energy sources exist’. Furthermore, since the mere presence of these does not necessarily lead to the emergence of life, this possibility only arises when these interact. Thus, it will also be suggested that the following can exist within the Goldilocks Edge: ‘The great prebiotic spot is an environmentally relaxed and semi-shielded area on an otherwise extreme world, wherein conditions advantageous for chemical evolution exist’. Such Goldilocks Edges and the great prebiotic spots within them can collectively represent the full distribution of possibilities for life in a solar system. Thus, the concept of a ‘limbus mundi’ or ‘world's edge’ is introduced.

Why did the emergence of our species require a timescale similar to the entire habitable period of our planet? Our late appearance has previously been interpreted by Carter (2008) as evidence that observers typically require a very long development time, implying that intelligent life is a rare occurrence. Here we present an alternative explanation, which simply asserts that many planets possess brief periods of habitability. We also propose that the rate-limiting step for the formation of observers is the enlargement of species from an initially microbial state. In this scenario, the development of intelligent life is a slow but almost inevitable process, greatly enhancing the prospects of future search for extra-terrestrial intelligence (SETI) experiments such as the Breakthrough Listen project.

Solutions to the Fermi paradox either deny the existence of extraterrestrials or offer alternative reasons to explain the non-occurrence of a first contact. While the latter, more optimistic approaches generally assume the existence of extraterrestrials, they simultaneously hint to limited future detectability. If solutions to the Fermi paradox are accepted as true, they must be evaluated in terms of how they affect the likelihood of success of future SETI efforts. Some solutions may lead to the so-called Fermi constraint: in order to explain why there has not been any contact so far, optimistic solutions to the Fermi paradox have to accept assumptions that, if the solution is assumed to be correct, indicate a very low probability of future contact. In other words: they are not here, and that is why they may never appear.

Although the field of synthetic biology is still in its infancy, there are expectations for great advances in the coming decades, both on Earth and potentially in space. Promising applications for long duration space missions include a variety of biologically engineered products and biologically aided processes and technologies, which will undoubtedly be scrutinized for risks and benefits in the broad context of ethical, legal and social realms. By comparing and contrasting features of Earth-based and space-applied synthetic biology, it is possible to identify the likely similarities and differences, and to identify possible challenges ahead for space applications that will require additional research, both in the short and long terms. Using an analytical framework associated with synthetic biology and new technologies on Earth, this paper analyses the kinds of issues and concerns ahead, and identifies those areas where space applications may require additional examination. In general, while Earth- and space-based synthetic biology share many commonalities, space applications have additional challenges such as those raised by space microbiology and environmental factors, legal complications, planetary protection, lack of decision-making infrastructure(s), long duration human missions, terraforming and the possible discovery of extraterrestrial (ET) life. For synthetic biology, the way forward offers many exciting opportunities, but is not without legitimate concerns – for life, environments and society, both on Earth and beyond.

Life has probably existed on Earth for about 3.5 billion years and ever since people could wonder, they have tried to understand its origins. It is thought that organisms as complex as bacteria emerged within 0.5–1 billion years. Organic molecules, such as amino acids, organic acids and sugars have been observed in material from extraterrestrial sources in the solar system. But, to confirm the possibility of nucleic acid bases also being synthesized under these conditions, we have replicated the synthesis of monophosphates as dry pellets (5′-monophosphates, the predominant reaction products) under simulated Martian conditions. Our research task was to find out whether the main organic substances were able to survive in the absence of water. This reaction must proceed under solvent-free conditions and incident short ultraviolet radiation (UVC) in a vacuum. After 5 months of reaction time monophosphates could be identified in detectable quantities. These experiments utilized basalt and limonite as protectors and successfully shielded the products from decomposition by UVC. Our team has obtained more results concerning prebiotic synthesis of polypeptides and nucleotides in the presence of meteorite dust; these are the same kind of experiment, but using different extraterrestrial material.

It has been suggested that Europa's subsurface environment may provide a haven for prebiotic evolution and the development of exotic biotic systems. The detection of hydrogen peroxide, sulfuric acid, water, hydrates and related species on the surface, coupled with observed mobility of icebergs, suggests the presence of a substantial subsurface liquid reservoir that actively exchanges materials with the surface environment. The atmospheric, surface and subsurface environments are described with their known chemistry. Three synthetic schemes using hydrogen peroxide, sulfuric acid and hydrocyanic acid leading to the production of larger biologically important molecules such as amino acids are described. Metabolic pathways based on properties of the subsurface ocean environment are detailed. Tidal heating, osmotic gradients, chemical cycling, as well as hydrothermal vents, provide energy and materials that may support a course of prebiotic evolution leading to the development or sustenance of simple biotic systems. Putative organisms may employ metabolic pathways based on chemical oxidation–reduction cycles occurring in the putative subsurface ocean environment.

The development of algorithms for agile science and autonomous exploration has been pursued in contexts ranging from spacecraft to planetary rovers to unmanned aerial vehicles to autonomous underwater vehicles. In situations where time, mission resources and communications are limited and the future state of the operating environment is unknown, the capability of a vehicle to dynamically respond to changing circumstances without human guidance can substantially improve science return. Such capabilities are difficult to achieve in practice, however, because they require intelligent reasoning to utilize limited resources in an inherently uncertain environment. Here we discuss the development, characterization and field performance of two algorithms for autonomously collecting water samples on VALKYRIE (Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice Explorer), a glacier-penetrating cryobot deployed to the Matanuska Glacier, Alaska (Mission Control location: 61°42′09.3″N 147°37′23.2″W). We show performance on par with human performance across a wide range of mission morphologies using simulated mission data, and demonstrate the effectiveness of the algorithms at autonomously collecting samples with high relative cell concentration during field operation. The development of such algorithms will help enable autonomous science operations in environments where constant real-time human supervision is impractical, such as penetration of ice sheets on Earth and high-priority planetary science targets like Europa.

We continue to investigate the binary system Kepler-16, consisting of a K-type main-sequence star, a red dwarf and a circumbinary Saturnian planet. As part of our study, we describe the system's habitable zone based on different climate models. We also report on stability investigations for possible Earth-mass Trojans while expanding a previous study by B. L. Quarles and collaborators given in 2012. For the climate models, we carefully consider the relevance of the system's parameters. Furthermore, we pursue new stability simulations for the Earth-mass objects starting along the orbit of Kepler-16b. The eccentricity distribution as obtained prefers values close to circular, whereas the inclination distribution remains flat. The stable solutions are distributed near the co-orbital Lagrangian points, thus enhancing the plausibility that Earth-mass Trojans might be able to exist in the Kepler-16(AB) system.

In previous work, a platform was developed for testing computer-vision algorithms for robotic planetary exploration. This platform consisted of a digital video camera connected to a wearable computer for real-time processing of images at geological and astrobiological field sites. The real-time processing included image segmentation and the generation of interest points based upon uncommonness in the segmentation maps. Also in previous work, this platform for testing computer-vision algorithms has been ported to a more ergonomic alternative platform, consisting of a phone camera connected via the Global System for Mobile Communications (GSM) network to a remote-server computer. The wearable-computer platform has been tested at geological and astrobiological field sites in Spain (Rivas Vaciamadrid and Riba de Santiuste), and the phone camera has been tested at a geological field site in Malta. In this work, we (i) apply a Hopfield neural-network algorithm for novelty detection based upon colour, (ii) integrate a field-capable digital microscope on the wearable computer platform, (iii) test this novelty detection with the digital microscope at Rivas Vaciamadrid, (iv) develop a Bluetooth communication mode for the phone-camera platform, in order to allow access to a mobile processing computer at the field sites, and (v) test the novelty detection on the Bluetooth-enabled phone camera connected to a netbook computer at the Mars Desert Research Station in Utah. This systems engineering and field testing have together allowed us to develop a real-time computer-vision system that is capable, for example, of identifying lichens as novel within a series of images acquired in semi-arid desert environments. We acquired sequences of images of geologic outcrops in Utah and Spain consisting of various rock types and colours to test this algorithm. The algorithm robustly recognized previously observed units by their colour, while requiring only a single image or a few images to learn colours as familiar, demonstrating its fast learning capability.

Over the last three years an outreach programme in astrobiology has been stimulating public interest in South Wales, UK. To date, 550 people have attended an accredited undergraduate course in astrobiology, Alien Worlds. Funded by a European Social Fund grant, this modular course has introduced students to the multidisciplinary nature of astrobiology, coupling academic content to a practical ability to recognise the constellations and objects of the night sky. This paper outlines the course's background, content, delivery and outcomes as an example of the outreach potential of the science and culture of astrobiology.

The concept of a rapid spread of self-replicating interstellar probes (SRPs) throughout the Milky Way adds considerable strength to Fermi's Paradox. A single civilization creating a single SRP is sufficient for a fleet of SRPs to grow and explore the entire Galaxy on timescales much shorter than the age of the Earth – so why do we see no signs of such probes? One solution to this Paradox suggests that self-replicating probes eventually undergo replication errors and evolve into predator-prey populations, reducing the total number of probes and removing them from our view.

I apply Lotka-Volterra models of predator-prey competition to interstellar probes navigating a network of stars in the Galactic Habitable Zone to investigate this scenario. I find that depending on the local growth mode of both populations and the flow of predators/prey between stars, there are many stable solutions with relatively large numbers of prey probes inhabiting the Milky Way. The solutions can exhibit the classic oscillatory pattern of Lotka-Volterra systems, but this depends sensitively on the input parameters. Typically, local and global equilibria are established with prey sometimes outnumbering the predators. Accordingly, we find this solution to Fermi's Paradox does not reduce the probe population sufficiently to be viable.

The Solar System passes within 5 pc of star-forming nebulae every ∼50–100 million years, a distance which can be bridged by protected micro-organisms ejected from the Earth by impacts. Such encounters disturb the Oort cloud, and induce episodes of bombardment of the Earth and the ejection of microbiota from its surface. Star-forming regions within the nebulae encountered may thus be seeded by significant numbers of microorganisms. Propagation of life throughout the Galactic habitable zone ‘goes critical’ provided that, in a typical molecular cloud, there are at least 1.1 habitable planets with impact environments similar to that of the Earth. Dissemination of microbiota proceeds most rapidly through the molecular ring of the Galaxy.

Water-soluble sulphate minerals such as epsomite and gypsum have been reported on a number of planetary bodies of astrobiological interest and their presence is often used as an indicator for potential habitability as it can indicate the presence of liquid water. The sulphate minerals can incorporate biomarkers and biomolecules as intracrystalline inclusions. These intracrystalline inclusions are protected from their exterior chemical environments and their analysis can yield a biomarker record, even in environments where extreme oxidizing conditions may have degraded any record present in non-intracrystalline organic matter. In this study, organic compounds were incorporated within epsomite as intracrystalline inclusions by co-precipitating a mineral from solutions of a mineral and organic compound. A feasibly study utilizing a microfluidic H-cell to process finely ground samples of the inclusion-bearing epsomite indicates that a similar device may be used to extract biomarkers for analysis.

The iconic Viking Landers that landed on Mars in 1976 demonstrated that the Martian surface is an extreme place, dominated by high UV fluxes and regolith chemistry capable of oxidizing organic molecules. From follow-on missions, we have learned that Mars was much warmer and wetter in its early history, and even some areas of Mars (such as crater lakes, possibly with sustained hydrothermal activity) were habitable places (e.g. Grotzinger et al. (2014). Science (New York, N.Y.) 343; Mangold et al. (2021). Science (New York, N.Y.). However, based on the Viking results we have learnt that the search for life and its remains is challenged by abiotic breakdown and alteration of organic material. In particular, the harsh radiation climate at the Martian surface that directly and indirectly could degrade organics has been held accountable for the lack of organics in the Martian regolith. Recent work simulating wind-driven erosion of basalts under Mars-like conditions has shown that this process, comparable to UV- and ionizing radiation, produces reactive compounds, kills microbes and removes methane from the atmosphere. and thereby could equally jeopardize the success of life-seeking missions to Mars. In this review, we summarize and discuss previous work on the role of physical and chemical mechanisms that affect the persistence of organics, and their consequences for the detection of life and/or its signatures in the Martian regolith and in the atmosphere.

The aim of this study is to increase our understanding of the attitudes towards the scientific search for extraterrestrial life among high school and university students in Sweden. The most important results of the analysis are that: (a) the great majority of students believe that extraterrestrial life exists; (b) most students regard searching for extraterrestrial life to be quite important or very important; (c) very few students think that we should actively avoid searching for extraterrestrial life; (d) the most common motive for assigning a high priority to search for extraterrestrial life is that it is interesting, the most common motive for assigning a low priority is that such knowledge would not be practically useful, or that the money would be better spent elsewhere; (e) most students do not think they are very well informed regarding the search for extraterrestrial life. A higher percentage of the students who judge themselves to be well informed also believe that extraterrestrial life exists. We have also found some differences between subgroups (men/women, high school students/university students and different fields of study), but the differences are with few exceptions small in comparison with the overall trends, and they mostly differ in degree rather than direction.