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The question about the stability of certain biomolecules is directly connected to the life-detection missions aiming to search for past or present life beyond Earth. The extreme conditions experienced on extraterrestrial planet surface (e.g. Mars), characterized by ionizing and non-ionizing radiation, CO2-atmosphere and reactive species, may destroy the hypothetical traces of life. In this context, the study of the biomolecules behaviour after ionizing radiation exposure could provide support for the onboard instrumentation and data interpretation of the life exploration missions on other planets. Here, as a part of STARLIFE campaign, we investigated the effects of gamma rays on two classes of fungal biomolecules–nucleic acids and melanin pigments – considered as promising biosignatures to search for during the ‘in situ life-detection’ missions beyond Earth.

The Moon is characterized by extremely harsh conditions due to ultraviolet irradiation, wide temperature extremes, vacuum resulting from the absence of an atmosphere and high ionizing radiation. Therefore, its surface may provide a unique platform to investigate the effects of such conditions. For lunar exploration with the Lunar Gateway platform, exposure experiments in Low Earth Orbit are useful testbeds to prepare for lunar space experiments and to understand how and if potential biomarkers are influenced by extra-terrestrial conditions. During the BIOMEX (BIOlogy and Mars EXperiment) project, dried colonies of the fungus Cryomyces antarcticus grown on Lunar Regolith Analogue (LRA) were exposed to space conditions for 16 months aboard the EXPOSE-R2 payload outside the International Space Station. In this study, we investigated the stability/degradation of fungal biomarkers in LRA after exposure to (i) simulated space and (ii) real space conditions, using Raman spectroscopy, gas chromatography-mass spectrometry and DNA amplification. The results demonstrated that fungal biomarkers were detectable after 16 months of real space exposure. This work will contribute to the interpretation of data from future biological experiments in the Cislunar orbit with the Lunar Gateway platform and/or on the lunar surface, in preparation for the next step of human exploration.

Astrobiology Graduates in Europe (AbGradE, pronounced ab-grad-ee) is an association of early-career scientists working in fields relevant to astrobiological research. Conceptualized in 2013, it was initially designed as a mini-conference or workshop dedicated to early-career researchers, providing a friendly environment where early-career minds would be able to present their research without being intimidated by the possibility of facing a more traditional audience, composed mainly of senior scientists. Within the last couple of years, AbGradE became the first point of call for European, but also for an increasing number of non-European, early-career astrobiologists. This article aims to present how AbGradE has evolved over the years (in its structure and in its way of organizing events), how it has adapted with the COVID-19 pandemic, and what future developments are considered. Version of record

The modern concept of the evolution of Mars assumes that life could potentially have originated on the planet Mars, possibly during the end of the late heavy bombardment, and could then be transferred to other planets. Since then, physical and chemical conditions on Mars changed and now strongly limit the presence of terrestrial-like life forms. These adverse conditions include scarcity of liquid water (although brine solutions may exist), low temperature and atmospheric pressure, and cosmic radiation. Ionizing radiation is very important among these life-constraining factors because it damages DNA and other cellular components, particularly in liquid conditions where radiation-induced reactive oxidants diffuse freely. Here, we investigated the impact of high doses (up to 2 kGy) of densely-ionizing (197.6 keV/µm), space-relevant iron ions (corresponding on the irradiation that reach the uppermost layer of the Mars subsurface) on the survival of an extremophilic terrestrial organism—Cryomyces antarcticus—in liquid medium and under atmospheric conditions, through different techniques. Results showed that it survived in a metabolically active state when subjected to high doses of Fe ions and was able to repair eventual DNA damages. It implies that some terrestrial life forms can withstand prolonged exposure to space-relevant ion radiation.

One of the primary current astrobiological goals is to understand the limits of microbial resistance to extraterrestrial conditions. Much attention is paid to ionizing radiation, since it can prevent the preservation and spread of life outside the Earth. The aim of this research was to study the impact of accelerated He ions (150 MeV/n, up to 1 kGy) as a component of the galactic cosmic rays on the black fungus C. antarcticus when mixed with Antarctic sandstones—the substratum of its natural habitat—and two Martian regolith simulants, which mimics two different evolutionary stages of Mars. The high dose of 1 kGy was used to assess the effect of dose accumulation in dormant cells within minerals, under long-term irradiation estimated on a geological time scale. The data obtained suggests that viable Earth-like microorganisms can be preserved in the dormant state in the near-surface scenario for approximately 322,000 and 110,000 Earth years within Martian regolith that mimic early and present Mars environmental conditions, respectively. In addition, the results of the study indicate the possibility of maintaining traces within regolith, as demonstrated by the identification of melanin pigments through UltraViolet-visible (UV-vis) spectrophotometric approach.

Cryptoendolithic microbial communities, discovered in the extremely cold, hyper-arid McMurdo Dry Valleys of Antarctica (Friedmann 1982), the most similar terrestrial environments to Mars surface (Wynn-Williams and Edwards 2000; Onofri et al., 2004), have been considered as a candidate in supporting the search of life in Mars exploration. In such harsh conditions, microorganisms grow in airspaces among mineral grains and show some adaptations, as the accumulation of protective pigments and compatible solutes, assuring their survival. In the frame of the Lichen and Fungi experiment (LIFE, P.I. Silvano Onofri; Onofri et al. 2012, 2015), small samples of these communities, were exposed to space, in the EXPOSE-E facility for 1.5 years, with an exposition to vacuum (10-7 to 10-4 Pa) (Horneck et al., 2010), galactic cosmic radiation (≤190mGy) (Berger et al., 2012), and the full spectrum of solar extraterrestrial electromagnetic radiation to which cryptoendolithic microorganisms demonstrated to survive (Scalzi et al., 2012). The search for trace of extant or extinct life is one of the main goals of the future space mission beyond Earth. The future rover missions ExoMars 2020 (ESA-Roscomos) and Mars 2020 (NASA) are exploring chemical and biological indicators of life, called biomarkers. A good biomarker must have a biogenic origin and thus must unequivocally be identified as possible trace of life. The detection of biomarkers on Mars was the aim of BIOMEX (BIOlogy and Mars Experiment) project, in which has been investigated the alteration of different biomarkers, after exposure to space and Mars-like conditions outside the International Space Station. In this contest, the aim of this work was to characterize fungal biomarkers from these exposed rock samples, with different approaches: i) Raman spectroscopy and InfraRed analyses, which has been considered excellent tools for the detection of inorganic and organic molecules, such as microbial pigments and ii) -omics approaches, as lipidomic and metabolomic techniques, performed to detect biological macromolecules and to determine their stability after space exposure. The focus of lipidomics and metabolomics has been on biomarker discovery, with the aim of identifying metabolites that are correlated with environmental exposures. The results suggest that microbial molecules can be detected through different techniques. In particular, our attention was focused on pigments, such as melanin and carotenoids that maintain their stability also after 1.5 years of space exposure. These results are of importance for the upcoming life-detection missions on Mars finalized for the search for past, extant or extinct life outside the Earth.