Nitsche, R. | bioRxiv Science

bioRxiv2026

ExocubeBio: an in-situ fluidic platform for microbial exposure on the International Space Station

Space-based platforms currently represent the most accurate means to experimentally assess the influence of the space environment on biological systems. However, performing such experiments remains technically challenging and requires highly specialized instrumentation. This study describes the current development and hardware qualification of ExocubeBio, a miniaturized experimental platform for in-situ biological space exposure. This experiment is scheduled for installation on the exterior of the International Space Station in 2027, as part of Exobio, the European Space Agencys new generation exobiology exposure facility. ExocubeBio will expose live microbial samples to the low Earth orbit environment, and combine autonomous in-situ optical density and fluorescence measurements, with the capacity to return preserved samples to Earth. Achieving these experimental goals requires a specialized, robust and reliable hardware system. The ExocubeBio hardware testing described here includes assessment of material biocompatibility and durability, functional validation of the miniaturized fluidic system, and optimization of the integrated optical subsystem for optical density and fluorescence measurements. These results demonstrate that the ExocubeBio experimental hardware components can each execute their core functional and operational requirements; subsystems allow for sample exposure, in-situ measurements of microbial cultures, and the chemical preservation of samples for post-flight analysis. As ExocubeBio transitions from hardware development to mission readiness, the results presented here validate the overall design and engineering approaches utilized. By combining the strengths of in-situ monitoring and sample return, ExocubeBio represents a significant advancement in space-based experimentation, and will provide new insights into microbial responses to the space environment.

microbiology↗

bioRxiv2025

Survival of NASA-cleanroom microbial isolates under simulated space and Martian conditions

Planetary protection hinges on understanding microbial survival following sterilization procedures, the stressors of space travel, and exposure to extraterrestrial environmental conditions. This study identified 23 fungal strains isolated from NASA-spacecraft assembly cleanrooms, capable of surviving ultraviolet radiation exposure. Using experimental simulation facilities, we conducted a comprehensive assessment of microbial survivability and morphology on the most resilient spacecraft-associated microorganisms. Aspergillus calidoustus demonstrated remarkable survival under simulated Martian conditions, withstanding up to 1440 minutes of Martian solar irradiation, Mars atmospheric pressure and composition, and the presence of Martian regolith. Lethality only occurred under combined irradiation and cooling to -60{degrees}C (the mean Mars surface temperature), emphasising the synergistic effect of these conditions. Furthermore, A. calidoustus survived long-duration neutron radiation exposure (replicating ionizing space radiation doses) and dry-heat sterilization (typically used for spacecraft components). This is the first study to perform an end-to-end evaluation of eukaryotic microbial survival across conditions that occur during preparation for, travel to, and robotic exploration of Mars. The experimental facilities and chronic exposure methods utilized offer a biologically meaningful model for understanding microbial risks during long-duration space missions. The capacity for fungal conidia to survive multiple space-relevant conditions suggests their potential as forward contaminants, capable of being transported to and persisting on Mars. As current spacecraft sterilization protocols prioritize bacterial spores, this research highlights a critical gap in planetary protection strategies. In addition to offering novel insights into microbial survival and dispersal, these findings have broader implications for biocontamination within the food, pharmaceutical, and medical sectors. ImportanceThis study reveals that conidia / spores of a fungus Aspergillus calidoustus, which was isolated from spacecraft assembly cleanrooms, can survive simulated space-relevant stressors like ultraviolet irradiation, Martian cold atmospheric pressure, regolith exposure, ionizing radiation and specific doses of recommended dry heat sterilization for spacecrafts. Such fungal resilience demonstrates that the species can survive certain space and Mars conditions previously thought to be sterilizing, highlighting a need to revise current spacecraft decontamination standards that focus mainly on bacterial spores. This study also highlights the need for continued microbial monitoring of spacecrafts during transit from Earth to other planets not only to achieve goals of planetary protection but also to maintain healthy closed system for manned missions. Moreover, it is also alarming for an Earth origin fungal species due to biocontamination risks for food, medical, and pharmaceutical industries may require need for new standards of sterilization approaches transferable to space exploration.

microbiology↗