Limits of Life and the Habitability of Mars: The ESA Space Experiment BIOMEX on the ISS

BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports—among others—the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit

Editorial: Microbial Communities of Polar and Alpine Soils

In recent years Arctic, Antarctic, and Alpine regions have experienced the highest rates of warming worldwide (Zemp et al., 2006; Anisimov et al., 2007). In Arctic and Alpine environments these phenomena are resulting in an increase of the duration of ice-free periods and an overall greening of terrestrial areas. The effects of warming on microbial decomposition of vast carbon pools in permafrost soils have the potential to cause a significant positive feedback to global climate change (Cavicchioli et al., 2019). Climate change in Antarctica, is firstly feared to result in the loss of unique and highly adapted ecosystems, mainly because of shifts in temperature and precipitation regimes, as well as longer term changes in edaphic profiles and the invasion of allochthonous, more competitive species (Convey and Peck, 2019). Soil microorganisms play a crucial role in mediating carbon and nitrogen balance and other biogeochemical cycles of global importance. Therefore, understanding the soil microbial diversity and ecology, including the ecological drivers that shape microbial communities, may be a key for understanding how biogeochemical cycles will respond to large-scale environmental and climatic changes. Given the key role of microorganisms in maintaining the balance of these environments, they could be viewed both as sentinels and amplifiers of global change (Maloy et al., 2016). In this framework, the e-book Microbial Communities of Polar and Alpine Soils aimed to collect original and noticeable research papers about diversity and functionality of soil microbial communities, their interactions with the other biotic components, including the aboveground plant coverage, and the abiotic factors determinant for the colonization of these habitats, as well their adaptation and resilience abilities to stressing conditions and environmental changes.2s