Human settlement in space brings with it interconnected biomedical challenges stemming from gravity, radiation, and temporal variability. Microgravity alters cellular processes, while cosmic radiation accelerates DNA damage. Furthermore, the absence of Earthly zeitgebers disrupts circadian rhythms and necessitates chronobiological adaptations. To overcome these challenges, interdisciplinary collaboration across physics, medicine, and molecular biology is essential to develop preventive strategies and ensure human health, survival, and evolution beyond Earth's boundaries.

This review provides a comprehensive analysis of acceleration mechanisms utilized in air-breathing electric propulsion, focusing on their fundamental principles, advantages, and the latest technological advancements. These thrusters, which utilize atmospheric gases to generate plasma and produce thrust, hold significant promise for very low Earth orbit missions due to their potential for high-efficiency propulsion. Central to their operation are the different mechanisms of acceleration. The review systematically categorizes the various acceleration mechanisms and discusses the physical principles behind these mechanisms, their integration into air-breathing propulsion architectures, and recent experimental efforts aimed at performance optimization.

Spaceflight stressors such as microgravity and radiation disrupt mitochondria in ocular tissues, leading to impaired energy production, oxidative stress, and reduced repair capacity. The anatomical distribution of mitochondria and disease localization presents an interesting relationship: cortical lens mitochondria align with the type of cataracts seen in spaceflight, while retinal mitochondria correspond to the pathology of SANS. These observations suggest mitochondrial damage may be more central to spaceflight-associated pathologies than previously recognized.

Understanding the shear and intrusion rheological behavior of granular materials under reduced gravitational conditions is crucial for applications in planetary exploration and submarine earthquake engineering. To this end, it is important to understand whether gravity affects the drag forces on objects intruding granular media and, if so, quantify these effects. We have studied this issue experimentally in 1 g and 0 g conditions, the latter using the Beijing Drop Tower. Measuring the resistive forces on a cylinder moving at a constant speed through a granular bed, we find that gravity plays a significant role - the resistive forces increase significantly with cylinder speed in 0 g, while increasing much more slowly in 1 g. We use Coupled Eulerian-Lagrangian (CEL) simulations that support our results. We attribute this behavior to the increasingly dominant effect of pressure-sensitive frictional forces in microgravity with increasing fluidity in these conditions. Other than the significant implications for extraterrestrial exploration, our findings suggest that constitutive modeling of flow in microgravity should differ significantly from that in 1 g.

Research on articular cartilage has primarily focused on athletes, particularly regarding increased metatarsal cartilage thickness in high-impact sports, with limited studies in military settings. This study examined Air Force Academy cadets, who experience unique mechanical demands on their hands. A total of 30 senior male cadets (age: 23.14 ± 0.51 years; height: 174.07 ± 3.14 cm; weight: 70.20 ± 6.63 kg) were evaluated based on their hand/wrist injury history, categorizing them into those with an injury history (IH; n,17) and non-injury history (NIH; n,13). Various assessments included body composition, hand grip strength, hand length, and ultrasonography, applying a validated tool (Michigan Hand Outcomes Questionnaire). Ultrasound measurements showed that the IH group had thicker cartilage than the NIH group in the index, ring, and little fingers, indicating the need for improved ergonomics in cockpit design and enhanced training protocols to mitigate injury risks among pilots.

Exposure to microgravity results in transient sensorimotor performance declines when crewmembers return to Earth, likely due to sensory re-weighting. This poses performance risks following gravitational transitions, such as arriving on the Moon or Mars. Here, we examined whether sensory brain network segregation (how independently a given network functions) in astronauts prior to an International Space Station mission would predict balance post-flight. Intraclass correlation analysis showed high test-retest reliability for all sensory network segregation measures. Indices of the Parietal Operculum 2 network (OP2) segregation pre-flight significantly predicted balance performance. Specifically, greater segregation predicted poorer balance on day one following return to Earth (Left OP2), better balance four days post-flight (Left and Right OP2) and greater balance improvements from one to four days post-flight. Results suggest that OP2 segregation may index plasticity of sensory weighting processes; that is, the degree of vestibular input down-weighting measured initially post-flight and extent of recovery over subsequent four days.

Spaceflight studies present novel insights into biological processes through exposure to stressors outside the evolutionary path of terrestrial organisms. Despite limited access to space environments, numerous transcriptomic datasets from spaceflight experiments are now available through NASA’s GeneLab data repository, which allows public access, encouraging further analysis. While various computational pipelines and methods have been used to process these transcriptomic datasets, learning-model-driven analyses have yet to be applied to a broad array of such spaceflight-related datasets. In this study, we present an open-source pipeline, GLARE: GeneLAb Representation learning pipelinE, which consists of training different representation learning approaches from manifold learning to self-supervised learning that enhance the performance of downstream analytical tasks. We illustrate the utility of GLARE by applying it to gene-level transcriptional values from the results of the CARA spaceflight experiment, an Arabidopsis root tip transcriptome dataset that spanned light, dark, and microgravity treatments. We show that GLARE not only substantiated the findings of the original study concerning cell wall remodeling but also revealed additional patterns of gene expression affected by the treatments, including evidence of hypoxic response. This work suggests there is great potential to supplement the insights drawn from initial studies on spaceflight omics-level data through further machine-learning-enabled analyses.

Spaceflight missions represent a new exposome, unpredicted by evolution. Life-threatening agents activate non-specific stress responses involving the psycho-immune-neuroendocrine network. The main molecular pathways regulating this network and those affected by spaceflight exposome/microgravity are reported in various experimental setups. They include gut microbiota-derived metabolites, potentially valuable for countermeasure development. Meaningfully, the application of neuromodulation techniques, like the non-invasive transcutaneous vagal stimulation, for the prevention of pathophysiological alterations related to stress responses, is discussed.

The La2O3-Nb2O5 binary system is a unique glass-forming system without conventional network former oxides, exhibiting two distinct glass-forming regions: La2O3-rich and Nb2O5-rich compositions. To evaluate its glass-forming ability, the temperature dependence of density, viscosity, and surface tension was measured using the electrostatic levitation furnace aboard the International Space Station (ISS-ELF). Melt density showed linear temperature dependence, and thermal expansion coefficients at 2000 K varied from 2.5 × 10-5 to 4.0 × 10-5 K-1. Substantial undercooling was observed for glass-forming compositions. Viscosity measurements above the melting point revealed that both La2O3-rich and Nb2O5-rich melts behave as fragile liquids. Activation energy derived from viscosity data was higher for glass-forming compositions. These results suggest that glass-forming ability can be assessed based on undercooling and activation energy across a wide compositional range, including non-glass-forming melts. The ISS-ELF experiments provide a valuable platform for understanding glass formation in systems inaccessible by terrestrial techniques.