In this comprehensive review, Acidithiobacillus ferrooxidans, an acidophilic bacterium, has been thoroughly examined as a plausible analogue for microbial life in Venus's lower cloud layer. Given its ability to adapt to extreme conditions, including low pH environments and metal-rich settings, Acidithiobacillus ferrooxidans is considered a promising candidate for studying life analogues in Venus's clouds. This article comprehensively analyses the bacterium's distinctive phenotypic and genotypic features, investigating its metabolic pathways, adaptive strategies and potential ecological niche within Venusian cloud ecosystems. After careful consideration of the environmental parameters characterizing Venus, the unidentified UV absorber in its clouds, and the prospects for microbial life, this review underscores the imperative nature of future Venus missions and the pivotal role that Acidithiobacillus ferrooxidans may play in exploring the possible habitability of Venus and advancing astrobiological research.

The question of whether extraterrestrials exist has driven both the search for extraterrestrial intelligence (SETI) and some attempts of messaging to extraterrestrial intelligence (METI). Nevertheless, no data-driven or theory-based behavioural policy has been suggested. Here we simulate a comprehensive set of human–extraterrestrial strategic interactions, modelled as two-by-two game-theoretic matrices. We examine a sample of possible outcomes by relying on the theory of subjective expected relative similarity (SERS), which takes into account both the expected payoffs and the extent of strategic similarity – the prospects of the opponent making identical choices. Simulation results suggest: focusing messaging efforts on signalling of complete strategic similarity, monitoring potential alien communications for similarity-indicating signals, and using risk-averse decision rules for policy planning and decision-making. The discussion puts forward three guidelines for METI initiatives and addresses the relevance of the findings to human conflict management.

Hemoglycin, a space polymer of glycine and iron, has been identified in the carbonaceous chondritic meteorites Allende, Acfer 086, Kaba, Sutter's Mill and Orgueil. Its core form has a mass of 1494 Da and is basically an antiparallel pair of polyglycine strands linked at each end by an iron atom. The polymer forms two- and three- dimensional lattices with an inter-vertex distance of 4.9 nm. Here the extraction technique for meteorites is applied to a 2.1 Gya fossil stromatolite to reveal the presence of hemoglycin by mass spectrometry. Intact ooids from a recent (3000 Ya) stromatolite exhibited the same visible hemoglycin fluorescence in response to x-rays as an intact crystal from the Orgueil meteorite. X-ray analysis confirmed the existence in ooids of an internal three-dimensional lattice of 4.9 nm inter-vertex spacing, matching the spacing of lattices in meteoritic crystals. FTIR measurements of acid-treated ooid and a Sutter's Mill meteoritic crystal both show the presence, via the splitting of the Amide I band, of an extended anti-parallel beta sheet structure. It seems probable that the copious in-fall of carbonaceous meteoritic material, from Archaean times onward, has left traces of hemoglycin in sedimentary carbonates and potentially has influenced ooid formation.

Amino acids have been detected in some meteorites and are readily synthesized in prebiotic experiments. These molecules may have been precursors of oligomers and polymers in the early Earth. These reactions were likely to happen in the protected confined spaces on the porous surface of olivine and in the interlayer nanospace of montmorillonite. This study describes experimental and theoretical research on the sorption of l-alanine onto surfaces of silicate minerals, olivine and montmorillonite. Kinetics of the sorption of this amino acid at different pH media was performed. This sorption has been also studied at atomic scale by means of quantum mechanical calculations finding that this sorption is energetically favourable. These results strongly support the premise that minerals could have actively participated in prebiotic reactions.

To deeply explore the solar system, it will be necessary to become less reliant on the resupply tether to Earth. An approach explored in this study is to convert hydrocarbons in asteroids to human edible food. After comparing the experimental pyrolysis breakdown products, which were able to be converted to biomass using a consortia, it was hypothesized that equivalent chemicals found on asteroids could also be converted to biomass with the same nutritional content as the pyrolyzed products. This study is a mathematical exercise that explores the potential food yield that could be produced from these methodologies. This study uses the abundance of aliphatic hydrocarbons in the Murchison meteorite (>35 ppm) as a baseline for the calculations, representing the minimum amount of organic matter that could theoretically be attributed to biomass production. Calculations for the total carbon in solvent-insoluble organic matter (IOM) represent the maximum amount of organic matter that could theoretically be attributed to food production. These two values will provide a range of realistic yields to determine how much food could theoretically be extractable from an asteroid. The results of this study found that if only the aliphatic hydrocarbons can be converted into biomass (minimum scenario) the resulting mass of edible biomass extractable from asteroid Bennu ranges from 5.070 × 107 g to 2.390 × 108 g. If the biomass extraction process, however, is more efficient, and all IOM is converted into edible biomass (maximum scenario), then the mass of edible biomass extractable from asteroid Bennu ranges from 1.391 × 109 g to 6.556 × 109 g. This would provide between 5.762 × 108 and 1.581 × 1010 calories that is enough to support between 600 and 17 000 astronaut life years. The asteroid mass needed to support one astronaut for one year is between 160 000 metric tons and 5000 metric tons. Based on these results, this approach of using carbon in asteroids to provide a distributed food source for humans appears promising, but there are substantial areas of future work.

Stars with about 45 to 80% the mass of the Sun, so-called K dwarf stars, have previously been proposed as optimal host stars in the search for habitable extrasolar worlds. These stars are abundant, have stable luminosities over billions of years longer than Sun-like stars, and offer favourable space environmental conditions. So far, the theoretical and experimental focus on exoplanet habitability has been on even less massive, though potentially less hospitable red dwarf stars. Here we present the first experimental data on the responses of photosynthetic organisms to a simulated K dwarf spectrum. We find that garden cress Lepidium sativum under K-dwarf radiation exhibits comparable growth and photosynthetic efficiency as under Solar illumination on Earth. The cyanobacterium Chroococcidiopsis sp. CCMEE 029 exhibits significantly higher photosynthetic efficiency and culture growth under K dwarf radiation compared to Solar conditions. Our findings of the affirmative responses of these two photosynthetic organisms to K dwarf radiation suggest that exoplanets in the habitable zones around such stars deserve high priority in the search for extrasolar life.

Germline gene editing (GGE) is a controversial procedure, prohibited by most intergovernmental and scientific bodies and is not currently medically utilized. However, given circumstances where GGE would be essential for human survival, it is possible that GGE could be ideal, ethical and even necessary. One such possible instance of this circumstance could be long-term presence of humans on other planets. In our paper, we point out that there is a strong case for genetically modifying humans, including through GGE, for a future settlement in space directed at preserving human (and other) species. To avoid unnecessarily suffering and death from such difficult missions and environments, GGE enhancements should be considered, although only if shown to be safe, well-regulated and efficacious. We also examine and detail how major ethical frameworks can be shown to support, rather than prohibit, such procedures.

Spacecraft can carry microbial contaminants from spacecraft assembly facilities (SAFs) to the cold arid surface of Mars that may confound life detection missions or disrupt native ecosystems. Dry hygroscopic sulphate and (per)chlorate salts on Mars may absorb atmospheric humidity and deliquesce at certain times to produce dense brines, potential sources of liquid water. Microbial growth is generally prohibited under the non-permissive condition of extremely low water activity in the frigid potential brines on Mars. Here we challenged the microbial community from samples of the Jet Propulsion Laboratory SAF with the extreme chemical conditions of brines relevant to Mars. Enrichment cultures in SP medium supplemented with 50% MgSO4 or 20% NaClO3 were inoculated from washes of SAF floor wipes. Samples were taken for each of the first four weeks and then at six months after inoculation to follow changes in the SAF microbial community under high salinity for long periods. Metagenomic DNA extracts of community samples were examined by Illumina sequencing of 18S rRNA gene sequences using fungal primers. The fungal assemblage during the first month of enrichment was predominantly common Ascomycetes, primarily Saccharomyete yeasts. Basidiomycetes were detected, mainly in the Microbotryomycetes and Tremellomycetes. Fungi were much less abundant in enrichment cultures at 50% MgSO4 than at 20% NaClO3. After 6 months of enrichment, few fungi remained. Microbes persisting from the JPL SAF microbial community in aged cultures enriched at extreme salinities might be the most capable of subsequently surviving and proliferating at the near surface of Mars. The SAF fungal assemblage did not survive and proliferate as well as the SAF bacterial community.

Amino acids are essential for the synthesis of protein. Amino acids contain both amine (R–NH2) and carboxylic acid (R–COOH) functional groups, which help to understand the possible formation mechanism of life in the universe. Among the 20 types of amino acids, glycine (NH2CH2COOH) is known as the simplest non-essential amino acid. In the last 40 years, all surveys of NH2CH2COOH in the interstellar medium, especially in the star-formation regions, have failed at the millimetre and sub-millimetre wavelengths. We aimed to identify the possible precursors of NH2CH2COOH, because it is highly challenging to identify NH2CH2COOH in the interstellar medium. Many laboratory experiments have suggested that methylenimine (CH2NH) plays a key role as a possible precursor of NH2CH2COOH in the star-formation regions via the Strecker synthesis reaction. After spectral analysis using the local thermodynamic equilibrium (LTE) model, we successfully identified the rotational emission lines of CH2NH towards the hot molecular core G10.47+0.03 using the Atacama Compact Array (ACA). The estimated column density of CH2NH towards G10.47+0.03 is (3.40 ± 0.2) × 1015 cm−2 with a rotational temperature of 218.70 ± 20 K, which is estimated from the rotational diagram. The fractional abundance of CH2NH with respect to H2 towards G10.47+0.03 is 2.61 × 10−8. We found that the derived abundance of CH2NH agree fairly well with the existing two-phase warm-up chemical modelling abundance value of CH2NH. We discuss the possible formation pathways of CH2NH within the context of hot molecular cores, and we find that CH2NH is likely mainly formed via neutral–neutral gas-phase reactions of CH3 and NH radicals towards G10.47+0.03.

The Fermi paradox points to the apparent contradiction between the idea that the emergence of life and civilization on Earth is an objective process following the general rules of Nature and that there are no visible signs of other civilizations beyond Earth. The Fermi paradox is widely discussed in astronomical, biological and other natural sciences but almost totally ignored by social sciences, even though more than half of known explanations deal with intentions and behaviours of extraterrestrial civilizations (ETCs) or social aspects of the evolution of technological civilizations. The article analyses the problem and possible solutions to the Fermi paradox from the perspective of social sciences. In this article I argue that the Fermi paradox is primarily a social science problem, and the most plausible solutions have to contain some form of social science explanations. Three types of explanations are discussed, namely, those related to ETCs’ intentions, capacities and the consequences of their decisions and activities. I argue that attempts to explain the paradox by referring to specific goals and motives of ETCs are the least plausible. Arguments related to the capacities and consequences are more solid but do not convincingly solve the paradox. I conclude that the Fermi paradox is an important problem for social sciences whether ETCs exist or not, and it should attract greater attention from social scientists.

Life as we know it requires the presence of liquid water and the availability of nutrients, which are mainly based on the elements C, H, N, O, P and S (CHNOPS) and trace metal micronutrients. We aim to understand the presence of these nutrients within atmospheres that show the presence of water cloud condensates, potentially allowing the existence of aerial biospheres. In this paper, we introduce a framework of nutrient availability levels based on the presence of water condensates and the chemical state of the CHNOPS elements. These nutrient availability levels are applied to a set of atmospheric models based on different planetary surface compositions resulting in a range of atmospheric compositions. The atmospheric model is a bottom-to-top equilibrium chemistry atmospheric model which includes the atmosphere–crust interaction and the element depletion due to the formation of clouds. While the reduced forms of CNS are present at the water cloud base for most atmospheric compositions, P and metals are lacking. This indicates the potential bio-availability of CNS, while P and metals are limiting factors for aerial biospheres.

The generation of organic compounds relevant to the origin of living beings is easily achieved if reducing conditions exist in the environment; however, proposed models of primitive atmospheres do not favour these conditions. This work considers the quantity and possible size of the cosmic bodies that could have impacted the Earth between 4.2 and 3.8 Ga. Different atmospheres (with gases such as CO2, CO, N2, CH4) were experimentally irradiated by an Nd-YAG laser (used to simulate the energy of a shock wave produced by the interaction of a cosmic body with the atmosphere). Although the main products are short-chain, saturated and unsaturated hydrocarbons, hydrogen cyanide (HCN) is the most abundant in some atmospheres. HCN is an important precursor of the organic molecules relevant to chemical evolution. According to our calculations, between 1023 and 1025 g of HCN could have been produced by the energy released to the atmosphere from the entry of cosmic objects between 4.2 and 3.8 Ga. Therefore, this shock wave energy could play an important role in the processes of chemical evolution.

A few dozens of solutions to the Fermi paradox have been proposed in the past. The most relevant ones will be concisely discussed in this paper. They will be classified as follows: exceptionality solutions, annihilation solutions and communication barrier solutions. The argument will be advanced that all existing resolutions to the Fermi paradox are in their essence anthropocentric. The epistemological groundwork of anthropocentrism will be discussed. Conversely, in this paper, a non-anthropocentric solution to the Fermi paradox will be proposed: the ‘lasting human epistemological limitations solution’. This resolution to the Fermi paradox acknowledges that human epistemological capacities are limited to the degree that not only extraterrestrial forms of life may be unobservable to the human perceptive apparatus, but that universes may exist around humans with forms of life, inorganic matter or entities of any other type that humans are incapable of perceiving. In light of the revolutionary developments in theoretical physics, it is likely that in the future these developments will be reflected in increasingly non-anthropocentric solutions to the Fermi paradox.

In situ elemental imaging of planetary surface regolith at a spatial resolution of 100s to 1000s of microns can provide evidence of the provenance of rocks or sediments and their habitability, and can identify post-depositional diagenetic alteration affecting preservation. We use high-resolution elemental maps and XRF spectra from MapX, a flight prototype in situ X-ray imaging instrument, to demonstrate this technology in rock types relevant to astrobiology. Examples are given for various petrologies and depositional/diagenetic environments, including ultramafic/mafic rocks, serpentinites, hydrothermal carbonates, evaporites, stromatolitic cherts and diagenetic concretions.

In a rapidly changing academic-scientific context, it is essential to adapt new learning strategies that foster the acquisition of new knowledge and the development of skills in future professionals, such as interacting synergistically with disciplines outside their own to execute projects successfully and comprehensively. The adaptation is only possible thanks to the inter and transdisciplinarity that Astrobiology has promoted since its inception. We use the term transdisciplinary for education that integrates different disciplines in a way to build new knowledge and increase the student's knowledge and skills. For this reason, this study aimed to demonstrate that an astrobiological stratospheric balloon launch project cultivates transdisciplinary awareness in participants: undergraduate university students in Lima, Peru. The sample consisted of 15 students from the following disciplines: biology, genetics, chemical engineering, physics, industrial engineering, agri-food engineering, forestry engineering, electronics engineering, mechatronics engineering, geology, geological engineering, philosophy, social communication, audiovisual communication and education. Using a semi-structured in-depth interview technique, experts validated the questions from the Universidad Nacional Mayor de San Marcos, Peru, and a matrix of meaning was constructed to classify the responses, ultimately obtaining the categories: contribution, complementarity and quantity. The participants' responses were processed and analyzed with Chat-GPT 3.5, revealing unanimous agreement that each participant's discipline contributed to the success of the balloon launch. To complement the qualitative interpretation of the results, a quantitative measurement was conducted to minimize subjective biases. Additionally, they gained knowledge and insights into other unfamiliar study subjects, collaborated to improve process quality, shared and harmonized their ideas to implement comprehensive solutions, and affirmed that their university education is often isolated or strictly focused on their specialization. In conclusion, experiences where different areas of knowledge converge in praxis, have the potential to awaken new technical, cognitive and communication skills in the individuals involved, utilizing astrobiological resources to invigorate and strengthen collective learning.

Astrobiocentrism is a vision that places us in a scenario of confirmation of life in the universe, either as a second genesis or as an expansion of humanity in space. It manages to raise consistent arguments in relation to questions such as what would happen to knowledge if life were confirmed in the universe, how would this change the way we understand our place in the cosmos? Astrobiocentrism raises a series of reflections in the context of confirmed discovery, and it develops concepts that work directly with what would happen after irrefutable evidence has been obtained that we are not alone in space. Unlike biocentrism or ecocentrism, the astrobiocentric view is not limited to the Earth-centric perspective, and for it incorporates a multi-, inter- and transdisciplinary understanding. Therefore, the aim of this paper is to make a reflection on the astrobiocentric issues related to the challenges and problems of the discovery of life in the universe and the expansion of mankind into space. Here we explore some aspects of the transition from biogeocentrism to astrobiocentrism, astrobiosemiotics, homo mensura, moral community, planetary sustainability and astrotheology.

Interplanetary spacecraft are built in a spacecraft assembly facility (SAF), a clean room designed to reduce microbial contamination that could confound life detection missions or influence native ecosystems. The frigid hyperarid near-surface environment of Mars has ample hygroscopic Mg and Na salts of chloride, (per)chlorate and sulphate that may deliquesce to form dense brines, liquids with low water activity, and freezing points <0°C. The current study sought to define the climax microbial community after 6 mo of enrichment of SAF floor wipe samples in salt plains medium supplemented with 50% (w/v; ~2 M; aw = 0.94) MgSO4 or 20% (w/v; ~1.9 M; aw = 0.91) NaClO3. After 1 wk, 4 wk and 6 mo of incubation, metagenomic DNA extracts of the enriched SAF microbial community were used for high-throughput sequencing of 16S rRNA genes and subsequent phylogenetic analyses. Additionally, dozens of bacterial strains were isolated by repetitive streak-plating from the climax community after 6 mo of enrichment. Early in the enrichment, staphylococci greatly dominated and then remained abundant members of the community. However, actinobacteria succeeded the staphylococci as the dominant taxa as the cultures matured, including Arthrobacter, Brachybacterium and Brevibacterium. A diverse assemblage of bacilli was present, with Oceanobacillus being especially abundant. The SAF culture collection included representatives of Brachybacterium conglomeratum, Brevibacterium sediminis, Oceanobacillus picturae and Staphylococcus sciuri. These were characterized with biochemical and physiological tests, revealing their high salinotolerance. Shannon diversity indices were generally near 2, reflecting modest diversity at several levels of identity and the community structures were uneven throughout. However, minor members of the community seem capable of the ecosystem functions required for biogeochemical cycling. For instance, organisms capable of all the functions of the N cycle were detected. The microbial assemblage in SAFs is the most likely to be transported by spacecraft to another world. While individual microbial populations may exhibit the qualities needed for survival at the near-surface of Mars, certainly entire communities with the capacity for complete biogeochemical cycling, would have a greater chance of survival and proliferation.

Although astrobiology studies how life functions and evolves, ecology is still largely overlooked in astrobiology research. Here we present an argument for astroecology, a merger of ecology and astrobiology, a self-aware scientific endeavour. Ecology is rarely mentioned in influential documents like the NASA Astrobiology Strategy (2015), and terms such as ‘niche’ can end up being used in a less precise fashion. As ecology deals with sequential levels of organization, we suggest astrobiologically-relevant problems for each of these levels. Organismal ecology provides ecological niche modelling, which can aid in evaluating the probability that Earth-like life would survive in extraterrestrial environments. Population ecology provides a gamut of models on the consequences of dispersal, and if lithopanspermia can be validated as a form of space dispersal for life, then metabiospheres and similar astrobiological models could be developed to understand such complex structure and dynamics. From community ecology, the discussion of habitability should include the concept of true vacant habitats (a misnomer, perhaps better called ‘will-dwells’) and contributions from the blossoming field of microbial ecology. Understanding ecosystems by focusing on abiotic properties is also key to extrapolating from analogue environments on Earth to extraterrestrial ones. Energy sources and their distribution are relevant for ecological gradients, such as the biodiversity latitudinal gradient – would tropics be species-rich in other inhabited planets? Finally, biosphere ecology deals with integration and feedback between living and non-living systems, which can generate stabilized near-optimal planetary conditions (Gaia); but would this work for other inhabited planets? Are there ‘strong’ (like Earth) and ‘weak’ (perhaps like Mars) biospheres? We hope to show ecology can contribute relevant ideas to the interdisciplinary field of astrobiology, helping conceptualize further levels of integration. We encourage new partnerships and for astrobiologists to take ecology into account when studying the origin, evolution and distribution of life in the universe.

In this study, we surveyed a total of 245 people about unidentified anomalous phenomena (UAP), 93 who directly witnessed UAP. Paying special attention to the psychological impact of UAP, our study survey covered different aspects, including opinions on official UAP releases, the scientific approach to the phenomena and the search for extra-terrestrial intelligence. This study found that UAP had a clear psychological impact on witnesses, with a transformative effect, and a benign form of a non-pathological obsessive-like interest in the topic we defined as the UAP deep psychological engagement triad. This deep psychological engagement triad is characterized by UAP topic being present in a witness's mind daily, with a self-recognized interest and appreciation for the topic and a need to talk about UAP topic, not necessarily the event they experienced. UAP appear to have a very specific impact focused on extra-terrestrial aspects and the phenomena itself, which is experienced as a life-changing event by direct witnesses. These psychological aspects are quantitatively and qualitatively objectifiable, and further research is needed in this direction since all research efforts appear currently focused on the physical aspects of these phenomena.