Extreme Life, Biospeology
and Astrobiology

The origin of life continues to represent one of the most complex and unresolved questions in modern science, necessitating the convergence of geochemistry, prebiotic chemistry, molecular biology, and evolutionary theory. This work explores the transformation from non-living chemical systems to the first biological forms, placing particular emphasis on the RNA world hypothesis and its connections to alternative models such as metabolism-first and lipid world scenarios. Available evidence supports the feasibility of RNA as an early biomolecule capable of fulfilling both informational and catalytic roles. Nonetheless, significant obstacles remain, including the prebiotic formation of nucleotides, the development of self-replicating ribozymes, and the achievement of high-fidelity replication under plausible environmental conditions. An increasing body of experimental and theoretical research points toward hybrid or co-evolutionary frameworks in which RNA, peptides, lipids, and protometabolic systems interacted from early stages and collectively facilitated the emergence of protocells. Comparative analyses of these competing models suggest that they are more appropriately interpreted as complementary elements within a multistage process, rather than as strictly competing hypotheses. Ongoing unresolved questions—such as the origin of the genetic code, the shift toward DNA–protein systems, and the coordination of replication with metabolism and compartmentalization—highlight the necessity for integrative, experimentally validated, system-level approaches. This study seeks to elucidate the current state of knowledge, identify major conceptual and experimental constraints, and underscore the critical role of integrative frameworks in advancing our understanding of the emergence of life.

This mini-review synthesizes current evidence regarding the effects of space radiation on cereal seeds, with emphasis on viability, germination, genetic integrity, and implications for extraterrestrial agriculture. Available data indicate that prolonged exposure to space radiation—particularly under low-shielding conditions—generally reduces seed viability and germination capacity, with marked interspecific variability, rice being more sensitive than barley or wheat. However, responses are heterogeneous, as some cereals exhibit enhanced germination under specific exposure scenarios, highlighting the complex interaction between radiation dose, quality, genotype, and environmental conditions. At the genomic level, space radiation induces DNA damage, chromosomal aberrations, and structural variation, supporting its application in mutation breeding programs. Orbital experiments aboard Mir and the International Space Station demonstrate that cereals can complete their life cycle in microgravity, although reproductive success is constrained by multiple interacting stressors, including atmospheric composition and system engineering limitations. For deep-space agriculture, current evidence remains insufficient, as low-Earth orbit (LEO) conditions do not fully replicate the radiation environment beyond Earth's magnetosphere. Emerging studies suggest that sustainable extraterrestrial crop production will require integrated strategies combining biological adaptation and physical radioprotection. Overall, space radiation represents both a risk factor for seed performance and a potential tool for crop improvement in future space-based agricultural systems.

The prospect of cultivating cereal crops on Mars represents a critical component of long-term extraterrestrial colonization and bioregenerative life support systems. This review synthesizes current evidence on the feasibility of cereal production under Mars-like conditions, focusing on key abiotic constraints including nutrient-deficient regolith, perchlorate toxicity, high salinity, water scarcity, and atmospheric composition dominated by CO₂. Studies using Martian regolith simulants (e.g., JSC-Mars-1A, MMS-1, MGS-1) consistently demonstrate that unamended substrates are incapable of supporting plant growth. In contrast, chemical and biological amendments, such as incorporating organic matter, adjusting pH, and introducing plant growth-promoting microorganisms, significantly improve outcomes. Perchlorate contamination remains a major unresolved barrier due to its persistence and phytotoxicity. Water treatment technologies, including desalination via cyanobacteria and plasma-activated water, show promise in enhancing plant performance. Although certain cereals, such as rye and wheat, have demonstrated partial growth success in amended simulants, no study has yet achieved full life-cycle cereal production under integrated Mars-like environmental conditions. The review highlights critical knowledge gaps, particularly regarding germination under low-oxygen, high-CO₂ atmospheres and the combined effects of multiple stressors, and outlines future research directions necessary for sustainable Martian agriculture.

Bioregenerative life support systems (BLSS) represent a critical technological pathway toward sustaining long-duration human space exploration by enabling the closure of material loops for air, water, food, and waste. This mini-review synthesizes current knowledge on the role of cultivated plants within BLSS architectures, emphasizing their multifunctional contribution as primary producers of edible biomass, oxygen generators, and agents of water purification. Key candidate species—including staple crops such as wheat, rice, potato, and soybean, as well as fast-growing plants like Wolffia globosa and microalgae—are evaluated in terms of productivity, nutritional value, and adaptability to space conditions. The review further examines nutrient recycling strategies, particularly nitrogen and phosphorus recovery from waste streams, and highlights the operational principles of major BLSS programs such as NASA’s CELSS and ESA’s MELiSSA. Special attention is given to the challenges of species selection under extraterrestrial constraints, including microgravity, radiation, and limited resources, as well as to emerging solutions involving extremotolerant microorganisms and in situ resource utilization (ISRU). Despite significant advances, current BLSS designs remain limited by incomplete nutrient closure and insufficient dietary completeness. Future progress will depend on the integration of biological and physicochemical subsystems, the optimization of crop systems for both yield and nutrition, and the validation of fully closed-loop systems at operational scale.

This mini-review examines the role of rhizosphere microbiomes associated with cereal crops as functional models for extraterrestrial agriculture within closed ecological systems. The rhizosphere microbiome, conceptualized as a plant’s “second genome,” plays a central role in nutrient acquisition, stress resilience, and disease suppression through complex plant–microbe interactions. The review synthesizes current knowledge on microbiome assembly, emphasizing the contributions of soil-derived, seed-borne, and host genotype-dependent microbial communities. Particular attention is given to biological nitrogen fixation and other nutrient-mobilizing processes mediated by plant growth-promoting microorganisms, which are critical in environments where synthetic inputs are limited. Furthermore, the paper explores microbiome-mediated mechanisms of abiotic stress tolerance, including hormonal regulation and metabolic adaptation under extreme conditions. Advances in microbiome engineering - such as synthetic microbial consortia, host-mediated selection, and microbiome transplantation - are discussed as strategies to enhance plant productivity in controlled and resource-constrained environments, including space-based greenhouses. Finally, key translational challenges are identified, including context-dependent inoculant performance, ecological compatibility, and the gap between laboratory findings and field application. The review highlights the necessity of integrating multi-omics approaches, precision breeding, and genome editing technologies to fully exploit microbiome-assisted agriculture for sustainable extraterrestrial food production.

Experimental astrobiology relies on laboratory simulation chambers to expose biological and chemical systems to controlled extraterrestrial analog conditions, including vacuum, ultraviolet irradiation, temperature extremes, pressure, and atmospheric composition. These facilities enable systematic isolation of individual stressors or selected combinations, thereby revealing causal mechanisms that remain inaccessible in the limited sample sizes and short-duration exposures of spaceflight experiments. Modern chambers integrate in situ spectroscopic and mass-spectrometric diagnostics, allowing real-time tracking of physicochemical and biological responses under Mars-, Titan-, Europa-, or interplanetary-space-relevant regimes. Biological assays demonstrate that certain extremophiles and lichens can tolerate partial analogs of Martian or low-Earth-orbit conditions, particularly when shielded by regolith or salts, whereas synergistic combinations of vacuum, UV, and thermal stress often produce far greater lethality than single-factor exposures. Chemical simulations successfully generate complex organics, including amino-acid and nucleobase precursors, from simple ices under vacuum-UV irradiation. Nevertheless, ground-based platforms cannot simultaneously reproduce the full coupled complexity of photon flux, ionizing particles, microgravity, long-term orbital history, and planetary-scale heterogeneity. Consequently, laboratory simulations remain indispensable complementary tools rather than complete substitutes for orbital or planetary exposure platforms. This mini-review synthesizes the capabilities, scientific yields, and irreducible limitations of current experimental approaches and highlights the continuing necessity of integrated laboratory-space research strategies.

Viruses constitute the most abundant biological entities on Earth, yet they remain markedly underrepresented in astrobiological research frameworks. This mini-review examines three interrelated dimensions of their relevance: their potential roles in the origin and early evolution of life, the constraints on their existence independent of complex ecosystems, and the challenges and opportunities they present for extraterrestrial life detection. Competing hypotheses - including viruses-first, viroids-first, and models situating viral emergence during the transition from the First Universal Common Ancestor to the Last Universal Common Ancestor - highlight viruses and virus-like entities as candidate participants in precellular evolution and as powerful drivers of subsequent cellular diversification. Although obligately dependent on host cellular machinery for replication, viruses display exceptional resilience in extreme terrestrial environments and under simulated interstellar conditions, suggesting that virions may persist where cellular life cannot. Detection of extraterrestrial viruses is currently hindered by the absence of validated biosignatures, instrument biases favoring cellular definitions of life, and limitations in metagenomic identification tools. Future missions targeting Mars or the subsurface oceans of icy moons offer unique opportunities to test viral origin hypotheses and to incorporate virus-aware detection strategies. Integrating virology into astrobiological thinking is therefore essential for a more complete understanding of life’s possible distribution and evolutionary trajectories beyond Earth.

The vegetation red edge (VRE) - a sharp increase in reflectance between approximately 700 and 750 nm arising from chlorophyll absorption of visible light and strong near-infrared scattering within leaf tissues - represents the most extensively studied surface biosignature for remote detection of photosynthetic life. This mini-review synthesizes current knowledge of terrestrial vegetation spectral signatures and their relevance to exoplanet biosignature searches. Earthshine and spacecraft observations have quantified the disk-integrated VRE as a few-percent feature whose strength varies with phase angle, cloud cover, and vegetated land fraction, requiring photometric accuracy of ~1% or better for reliable detection. Temporal variability linked to seasonal growth and senescence provides a critical discriminant against abiotic mineral edges. Complementary biosignatures, including circular spectropolarimetry rooted in molecular homochirality and photosynthetic fluorescence, offer independent confirmation pathways that reduce false-positive risk. Detectability on exoplanets depends on host-star spectral energy distribution, cloud fraction, surface coverage, and evolutionary stage of any biosphere; models indicate that VRE-like features could be recoverable on nearby rocky worlds with exposure times of tens to hundreds of hours under favorable conditions. Extrapolation to extraterrestrial environments is further informed by aquatic floating vegetation, extreme-environment analogues, and considerations of prebiotic chemistry. Collectively, these findings underscore that robust life detection will require multi-wavelength, time-resolved, and multi-technique observations rather than reliance on any single spectral feature.