Saturn's moon Titan exhibits remarkable parallels to the Earth in many geophysical and geological processes not found elsewhere in the solar system at the present day. These include a nitrogen atmosphere with a condensible gas - methane - replacing the Earth's water, leading to an active meteorology with rainfall and surface manifestations including rivers, lakes and seas, and the dissolution of karstic terrain. Other phenomena such as craters, dunes, and tectonic features are found elsewhere - e.g. on Mars and Venus - but their continuing alteration by pluvial, fluvial and lacustrine processes can be studied only on Earth and Titan. Meanwhile Titan also hosts an interior liquid water ocean with similarities to the Earth as well as to ocean worlds such as Europa and Enceladus. Our focus in this review paper is twofold: to describe the geophysical and geological parallels between Earth and Titan, and to evaluate the yet-underexploited possibilities for field analog research to gain new knowledge about these processes. To date, Titan's much colder temperature and different atmospheric and crustal materials have led to a skepticism that useful analogs can be found on Earth. Our conclusion, however, is that a much larger range of useful analog field work is possible and this work will substantially enhance our knowledge of both worlds. Such investigation will supplement the existing sparse data for Titan returned by space missions, will greatly enhance our understanding of such datasets, and will help to provide science impetus and goals for future missions.

The ambiguity of the Viking lander life-detection experiments left microbiology and microbial ecology out of space missions for 50 years. However, this was largely because the scientific process inherent in the search for life was misunderstood by a space exploration community that wanted clear-cut answers. Since Viking, enormous advances have been made in our knowledge of microorganisms, their biochemistry, and physical and chemical limits. Coupled with improvements in methods for culturing microorganisms and measuring their active metabolism, this has made possible more sophisticated experiments to search for life in extreme environments on Earth and on other planetary bodies. By overcoming misunderstandings surrounding the Viking lander experiments, microbiology and microbial ecology can take center stage in renewed efforts to seek life elsewhere. Furthermore, new knowledge in these fields should be used to overhaul assumptions in planetary protection, and it can be used to achieve permanent human space settlement.

Geological materials are often seen as the antithesis of soft; rocks are hard. However, during the formation of minerals and rocks, all the systems we shall discuss, indeed geological materials in general, pass through a stage where they are soft. This occurs either because they form at a high temperature - igneous or metamorphic rock - or because they form at a lower temperature but in the presence of water - sedimentary rock. For this reason it is useful to introduce soft-matter concepts into the geological domain. There is a universality in the diverse instances of geological patterns that may be appreciated by looking at the common aspect in their formation of having passed through a stage as soft matter.

Postimpact recovery and evolution in response to climate changes produced a modern ecosystem at Meteor Crater dominated by a grassland and woodland of pi & ntilde;on and juniper, which has been used to evaluate floral and megafaunal consequences of impact cratering during the Phanerozoic Eon of complex life. Here, we describe a postimpact endolithic community that illustrates a potential habitat for micro-ecosystems around impact craters in both Proterozoic and Phanerozoic times. Phototrophs within impact-ejected carbonate are dominated by eukaryotic green algae that affiliate with Trebouxiophycaea (Trebouxia and Stichococcus spp.). Eukaryotic fungi are dominated by Ascomycota, including Hydropisphaera, Trichoderma, Acremonium, and Stanjemonium spp., and representatives of Basidiomycota including Agaricomycetes and Clitopilus spp. The prokaryotic community is dominated by Actinobacteria and Proteobacteria, the latter dominated by Alphaproteobacteria. At a genus level, the bacterial community contains typical representatives of soil and rock environments, including Promicromonospora, Lentzea, Streptomyces, Kribella, Rubrobacter, Deinococcus, Sphingomonas, Belnapia, and Methylobacterium spp. These data show that impact crater rocks host taxonomically diverse communities potentially involved in carbon cycling in the early stages of colonization.

Expanding human space exploration necessitates technologies for sustainable local resource acquisition, to overcome unviable resupply missions. Asteroids, some of which rich in metals like platinum group elements, are promising targets. The BioAsteroid experiment aboard the International Space Station tested the use of microorganisms (bacteria and fungi) to extract 44 elements from L-chondrite asteroidal material under microgravity. Penicillium simplicissimum enhanced the release of palladium, platinum and other elements in microgravity, compared to non-biological leaching. For many elements, non-biological leaching was more effective in microgravity than on Earth, while bioleaching remained stable. Metabolomic analysis revealed distinct changes in microbial metabolism in space, particularly for P. simplicissimum, with increased production of carboxylic acids, and molecules of potential biomining or pharmaceutical interest in microgravity. These results demonstrate the impact of microgravity on bioleaching, highlighting the need for optimal combination of microorganisms, rock substrate, and conditions for successful biomining, in space and Earth.

Over the last several decades, investigations of Earth's subsurface and other extremely low-biomass systems have refined our understanding of the environmental limits of life, driven by methodological advances that permit agnostic life detection of biology and their respective physical biosignatures and chemical biomarkers. These advances enable mission concepts centered on microbiological processes that facilitate identification of both active life and preserved biosignatures through measurements of metabolism and associated biochemical markers that, on Mars, are more likely to be retained below the surface. Terrestrially, although biological processes can exert a significant influence on Earth's crust, the presence of habitable conditions does not necessarily imply the existence of cellular life. The Viking missions constituted the first direct life-detection experiments on Mars but produced equivocal outcomes, prompting subsequent exploration strategies to emphasize surface habitability rather than direct biological testing. Leveraging progress in subsurface microbiology and planetary exploration, we contend that Mars missions are now poised to shift toward direct tests for extant microbial activity in the subsurface, with metabolic processes serving as a broadly applicable indicator of life.

Ocean worlds are important targets for life detection missions because they meet several key requirements for habitability. However, identifying potential life requires observing clear and unambiguous biosignature signals above the baseline of existing abiotic processes, which are rarely characterized rigorously enough to adequately evaluate this risk. Here we develop a quantitative framework for holistically evaluating abiotic baselines on ocean worlds to guide life detection strategies. Using Enceladus as an example, we assess the potential of using CH4 isotopes and their relationship with CO2, and amino acid chirality as biosignatures, demonstrating that uncertainties in abiotic processes currently prevent hypothetical future delta C-13(CO2) and delta C-13(CH4) measurements from definitively inferring a biosphere on Enceladus. Neglecting the abiotic baseline thus risks ambiguous and false negative life detection claims for isotopic and chiral biosignatures, respectively. Interpreting these and other alternative biosignatures on Enceladus, Europa, Titan and similar planetary bodies therefore requires complementary geophysical observations. Abiotic ambiguity can be reduced by constraining internal temperatures to within similar to 10-100 degrees C and improving characterization of the target's rheology, lithology, initial abiotic organic inventory and ocean transport timescales.

BackgroundBiotechnological advances are transforming the potential for sustainable resource utilization in space exploration. Biomining, using microorganisms to extract valuable metals, has emerged as a viable strategy for in situ resource utilization (ISRU) in extraterrestrial environments. However, an increasing body of literature is showing that selecting the most efficient bioleaching approach highly depends on the interaction between the microbial species, the type of rock and environmental conditions. In the space biomining context, the heterotrophic bacterium Sphingomonas desiccabilis has demonstrated its capacity to extract valuable metals in space.MethodsThis study harnessed a comparative bioleaching analysis to investigate the organism’s ability to extract industrially relevant metals from seven terrestrial and extraterrestrial rock types, including a meteorite, a basaltic rock, and samples from the Sudbury Basin, an impact structure formed ~1.85 Ga ago.ResultsWe demonstrated that, depending on the substrate mineralogy, S. desicca bilis selectively mobilized Ce (up to 10.6%), Th (up to 1.5%), and other metals such as Pd, Pt, Mo, and W, at circum-neutral pH conditions. However, the extraction was not equal across all substrates, indicating the importance of mineralogy in bioleaching.DiscussionWhile extraction rates were lower compared to industrial biomining standards, these results underscore the organism’s potential in low-grade rocks bioleaching, particularly relevant for sustainable terrestrial biomining and long-duration space missions. More broadly, this work demonstrates that bioleaching efficiency is shaped not only by the microbial species employed, but also by the specific characteristics of the substrate, emphasizing the need to tailor bioleaching strategies to distinct mineral contexts.

Abstract Kerogen, insoluble macromolecular organic matter in sedimentary rocks, is the most abundant form of organic carbon on Earth and plays a role in deep biosphere processes. It is classified into four types (I–IV) based on origin and chemical composition, yet its influence on microbial communities and carbon cycling remains poorly understood. In this study, we examined how kerogen-rich shales and coals, each containing a distinct kerogen type, shape anaerobic microbial community development and activity. CFU counts showed that kerogen types I and II did not significantly alter overall microbial abundance, while type III-rich rocks inhibited growth, and type IV-rich rocks enhanced it. 16S rRNA gene sequencing revealed that type II-rich rocks selectively enriched for Burkholderiaceae, whereas type IV-rich rocks promoted the proliferation of Cellulomonadaceae and Pleomorphomonadaceae. Gas chromatography showed that CO2 production occurred only in the presence of type II-rich rocks, likely driven by Burkholderiaceae activity. These findings suggest that kerogen structure and geochemical properties drive microbial community assembly and organic matter mobilization in the deep subsurface. Beyond Earth, kerogen type IV-like material is widespread in extraterrestrial environments. Our results indicate the enhancement of the habitability of these environments, offering new insights into the potential for life.

One underexplored aspect of microbial growth is the impact of toxic gases transported through the atmosphere. Ammonia is a gas that can supply essential nitrogen but also exert cellular toxicity. Ammonia volatilized from a concentrated source into surrounding environments is therefore a crucial consideration when assessing the capacity of environments to support life, such as within terrestrial environments polluted with ammonia, or the ice crusts above ammonia–water oceans of icy moons. We cultivate Halomonas meridiana proximal to an ammonia source and examine the impact of ammonia volatilization on growth. Lower cell densities (OD600 = 0–1) occurred nearest the ammonia source. At 24 h, wells exhibiting an OD600 = 0–0.5 were evident when ammonia concentrations were ≥ 0.5 M. H. meridiana in proximity to 0 M, 0.1 M, 0.25 M, 0.5 M, and 1 M ammonia exhibited OD600 > 2 in 89.86

In Arctic polar deserts, rocks can be extensively colonized by phototrophic hypolithic communities that exploit periglacial sorting processes to grow beneath opaque rocks. These communities are distinguished by green bands that are distinctly and abruptly separated from the black-pigmented communities on the rock surface (epiliths). We used 16S and 18S rDNA culture-independent methods to address the hypothesis that the two communities are different. Although both communities were dominated by cyanobacterial species (Chroococcidiopsis and Nostoc spp.), we found that the hypolithic and epilithic habitats host distinct microbial communities. We found that eukaryotic hypolithic and epilithic communities were statistically similar but that the hypolithic habitats contained tardigrade DNA, showing that the more clement subsurface habitat supports animal life in contrast to the surface of the rocks. These results reveal the distinctive communities and sharp demarcations that can develop across small spatial scales in the Earth's rocky extreme environments.

One key objective of astrobiology is to investigate and discover if other planetary bodies are habitable. The determination of whether an environment is habitable to known life requires measuring liquid water, CHNOPS elements, other nutrients, and energy supplies. Here we investigate the potential for a single instrument capable of sampling these key indicators: a ‘Total Habitability Instrument’. The proposed instrument would be capable of deployment in diverse environments and provide an integrated set of measurements that together allow for the assessment of the habitability of an environment of interest, such as those of the Moon or Mars. We explore existing and potential technological developments that would enable the construction of such an instrument, with a focus on soft systems, which are inspired by nature in their design, and microfluidics. This paper considers a multidisciplinary approach to the design and sensing requirements of a Total Habitability Instrument that would be capable of gathering and processing samples and be deployable by both robotic and human explorers on all planetary bodies, allowing for the mapping of habitability over large areas of our Solar System and beyond.

Although a large fraction of Earth's volume and most places beyond the planet lack life because physical and chemical conditions are too extreme, intriguing scientific questions are raised in many environments within or at the edges of life's niche space in which active life is absent. This review explores the environments in which active microorganisms do not occur. Within the known niche space for life, uninhabited, but habitable physical spaces potentially offer opportunities for hypothesis testing, such as using them as negative control environments to investigate the influence of life on planetary processes. At the physico-chemical limits of life, questions such as whether spaces devoid of actively metabolizing or reproducing life constitute uninhabitable space or space containing vacant niches that could be occupied with appropriate adaptation are raised. We do not know the extent to which evolution has allowed life to occupy all niche space within its biochemical potential. The case of habitable extraterrestrial environments and the scientific and ethical questions that they raise is discussed.

We reconsider the problem of planetary protection using, by the analogy of planets as islands, the theory of island biogeography. We show that although the notion of equilibrium populations that emerge from the effects of immigration and extinction generally breaks down when applied to interplanetary scales, the mean-time to extinction resulting from the combined effects of growth and death rates can be quantified. We reconsider the probabilistic model of planetary protection, discuss how mean-time to extinction can instead be used to assess contamination risk, and we propose a research direction for planetary protection based on these ideas. We discuss more broadly the applicability of island biogeography to considering biotic transfer at interplanetary scales.

Sustaining life beyond Earth requires the creation of habitats, which is typically assumed to require costly transport of high-mass components from Earth. Here, we investigate an alternative approach based on in situ fabrication using biologically generated materials. We show that several common biomaterials are capable of blocking UV radiation, transmitting visible light, and maintaining pressure differences sufficient to permanently stabilize liquid H2O in a vacuum or low-pressure environment. As a proof of concept, we then demonstrate growth of eukaryotic green alga in a 3D printed PLA bioplastic habitat under Mars-relevant conditions of a 600 Pa CO2 background atmosphere. Our results demonstrate that products of biology itself can be used to create habitats in extraterrestrial environments. This approach is scalable, sustainable, and plausibly could be extended to construction of human habitats in the future.

Fullerenes of extra-terrestrial origin may have been accessible as carbon sources for anaerobic microorganisms on the early Earth. Very little is known about how anaerobic microorganisms respond to and use fullerenes and their soluble derivatives. We present an investigation into the effects of fullerenes C60 and C70 and their hydroxylated fullerol derivatives on an environmentally relevant anaerobic community and a microbial isolate. Fullerenes and fullerols irradiated with 254 nm UV radiation for 2 weeks in the absence of oxygen to simulate UV irradiation under anoxia on early Earth were also assessed. The anaerobic community could grow using glucose in the presence of C60 up to 500 mg/mL without inhibitory effects on growth. Concentrations of C70 of 500 mg/ml were inhibitory. We attribute these results to the different chemical reactivity and photophysical properties of the fullerenes. The experiments suggest the potential for the use of C60 as a sole carbon source. Both C60 and C70 fullerols were inhibitory to growth in the presence of glucose, especially when exposed to light. When we exposed C60 fullerol suspensions to 254 nm UV radiation under an anoxic atmosphere, they become significantly more inhibitory to both the community and the isolate, but only if the cultures are grown under ambient light exposure. The anaerobic isolate was unable to grow on C60 alone, but after UV radiation exposure, the C60 photodegradation products served as a potentially accessible carbon source. Our data show that fullerenes and their derivatives are biologically active and capable of influencing growth in anoxic environments such as those that would have been prevalent on early Earth or in modern-day anoxic soils. Our results show that carbon sources such as these can be both beneficial or deleterious to life depending on their concentrations and environmental processing.

Polygonal structures, some of which are formed in salt deposits, have been documented at numerous locations on the surface of Mars, clearly visible from orbit with high-resolution imaging systems and spectral techniques. Based on a terrestrial analog, these deposits are potential locations to harbor biomarkers, which play a key role in the search for extraterrestrial life. This study examines the measurement capabilities of a laser-based mass spectrometer for the chemical composition analysis of such polygonal structures found in the Boulby Mine, United Kingdom, a Mars analog site. A space-prototype laser ablation ionization mass spectrometry system was used to measure the elemental composition of the material. The analysis for potentially habitable conditions and the presence of preserved biomarkers is based on the abundance of the CHNOPS elements in the halite host. In total, six samples, three from the edge and interior, respectively, of various polygons were investigated. The chemical analysis showed that the edges of polygonal structured salt deposits are preferential sites for element accumulation, with a higher abundance in CHNOPS elements and other trace elements necessary for the formation and maintenance of life. Polygonal structures might be alternative landing sites for future in situ space exploration missions devoted to life detection. The availability and ability to interpret imaging data from orbit enable an easy targeting of polygon structures, thus improving the selection for a landing site with higher potential to detect biosignatures and reducing mission costs by deploying dedicated instrumentation for in situ analysis.

The search for signatures of life beyond Earth has been a primary motivator in the field of space science. The question of the ideal exploration site for the search of such signatures for life remains unanswered, despite an increase in space missions dedicated to the understanding of the formation of the Martian surface and its environmental history. The present space exploration missions focus on formerly subaqueous environments, such as water bodies and deltaic structures [1,2]. While these sites have the capability to bury organic material due to rapid sedimentation, the preservation of biosignatures in those high-energy settings is often compromised by oxidizing fluids and gases [3]. Conversely, tranquil settings, such as ancient lakes, might be more suited for biomarker preservation. Many of these lakes were saline and formed salt deposits when they dried out. During salt precipitation, biomarkers can be buried and shielded from the harsh radiation prevailing on the Martian surface. Thus, these evaporites have been previously suggested as important sites for the search for life on Mars [4]. Such salt deposits on the surface of Mars have been identified numerously, displaying distinctive polygonal surface features, visible from orbit by e.g., CRISM or HiRISE imaging [5]. Similar polygonal structures are also found at Mars analogue sites in salt deposits on Earth, like in the Atacama Desert [6] or in the Boulby Mine, United Kingdom. This contribution presents the results of our study focused on the polygonal structures within the halite deposits of the Boulby Mine. The measurements were performed using a space-prototype laser ablation ionisation mass spectrometer (LIMS) [7,8]. The polygons show two optically distinct features, consisting of dark edges and light interiors. For both features, interior and edge, the chemical composition was determined using LIMS and compared. A specific focus was placed on the difference in abundance of the CHNOPS elements, as they serve as biomarkers. A significant increase in CHNOPS and other biologically relevant minor and trace elements, necessary e.g., for the maintenance and formation of life, was observed at the polygonal edges. This shows that the edges of polygonal structured salt deposits are preferential sites for element accumulation. As a result, the edges of salt deposits might be more habitable to life as we know it and could serve as promising sites for detecting signatures of life in future in-situ space exploration missions. [1] Mangold, N. et al., 2020, https://doi.org/10.1089/ast.2019.2132[2] Vasavada, A. R., 2022, https://doi.org/10.1007/s11214-022-00882-7[3] Hays, L. E., 2017, https://doi.org/10.1089/ast.2016.1627[4] Rothschild, L. J., 1990, https://doi.org/10.1016/0019-1035(90)90188-F[5] El-Maarry, M. R. et al., 2013, https://doi.org/10.1002/2013JE004463[6] Sager, C. et al., 2021, https://doi.org/10.1016/j.geomorph.2020.107481[7] Riedo, A. et al., 2012, https://doi.org/10.1002/jms.3104[8] Tulej, M. et al., 2021, https://doi.org/10.3390/app11062562

At the present stage of the development of human civilization the rapid development of high-tech space technologies, growing scientific and commercial interest in space, and also increased attention to fundamental questions about the origin and future of life in the Universe require the formation of new scientific efforts regarding the understanding of the phenomenon of life, the emergence of the biosphere, and the planetary role of man in the further evolution of planet Earth. Modern society is actively seeking answers to lifelong questions related to whether our biosphere is the only form of life in space, and whether human contact with extraterrestrial life forms and civilizations is possible. The search for these answers is facilitated by such a science as astrobiology. The purpose of this publication is a brief overview of the current state of astrobiology based on publications in leading scientific journals over the past decades, as well as an analysis of the potential opportunities for the development of this science in Ukraine. Astrobiology as a science is an interdisciplinary field that studies the question of the origin of life on Earth, how it has evolved on this planet for billions of years, its limits, and the existence of life beyond Earth, its possible forms and modes of life existence, as well as the conditions for the emergence and development of life in the Universe. Astrobiology investigates whether life, as a cosmic phenomenon, can exist beyond Earth in various forms, including terrestrial ones delivered by spacecraft to other planets. The main goal of astrobiology is to search for and study various forms of life beyond Earth, as well as to study the existence of terrestrial life forms in extreme conditions, close to the conditions of open space and environmental conditions on other planets of the Solar and other stellar systems. An important interdisciplinary area of research in modern astrobiology is the study of the chemical composition of interstellar space and chemical processes that can lead to the formation of organic molecules. Abiogenic synthesis of organic compounds in outer space can occur under conditions of extremely low temperatures, cosmic vacuum and high levels of ionizing radiation. The theory of the spontaneous origin of life on planet Earth suggests that the first simplest living organisms arose by self-organization from organic compounds that were formed as a result of their abiogenic synthesis. The possibility of abiogenic synthesis of biologically relevant organic molecules has been experimentally proven. But the idea of the spontaneous origin of life as a molecular-informational phenomenon still remains hypothetical. The alternative viewpoint is a theory of panspermia. This theory assumes the process of spontaneous origin of life somewhere else in space, such as on another planetary body, and living organisms came to Earth with space dust, comets and asteroids. The possibility that organisms can survive movement through space is supported by some experimental confirmation based on studies of the resistance of certain types of organisms to extreme factors of open space and environmental conditions on some planets and satellites, in particular on Mars, Enceladus and other celestial bodies. An important area of research in modern astrobiology is the search for biosignatures that can reliably indicate the presence of certain life forms. The development of astrobiology gives rise to a number of systemic issues that must be resolved and which should form a systemic vision of the possibility of the existence of various life forms on other planets. An important issue in astrobiology is the problem of the influence of cosmic factors on the terrestrial biosphere and possible biospheres of other planets. These factors are primarily associated with the activity of stars around which planetary systems are formed. In connection with the active development of space missions to the planets of the Solar System, the question arose of the possibility of transferring terrestrial life forms on space probes to other planets, which in turn raises a number of problems associated with astrobiological "pollution" and the ethical responsibility of human civilization for the spread of terrestrial life forms as a result of contamination of space probes. The review pays special attention to the issues of training highly qualified specialists in the field of astrobiology at universities and relevant educational and scientific centers, in particular on the basis of the UK Astrobiology Center of the University of Edinburgh. The need to open an International Astrobiology Center on the basis of Taras Shevchenko National University of Kyiv together with the University of Edinburgh is substantiated. Astrobiology is a new, interdisciplinary, and in-demand science. It has its own scientific challenges and methodology. The further development of this field of knowledge requires the involvement of specialists from various natural and humanitarian disciplines, who need to be trained through new interdisciplinary educational courses and programs for the preparation of bachelors, masters, and doctors of philosophy