The Ground-Based BIOMEX Experiment Verification Tests for Life Detection on Mars.

Claudia Pacelli,Alessia Cassaro,Alessandro Maturilli,Ilaria Catanzaro,Mickael Baqué,Ute Böttger,Elke Rabbow,Silvano Onofri,Jean-Pierre Paul De Vera

doi:10.3390/life11111212

Abstract

The success of an astrobiological search for life campaign on Mars, or other planetary bodies in the Solar System, relies on the detectability of past or present microbial life traces, namely, biosignatures. Spectroscopic methods require little or no sample preparation, can be repeated almost endlessly, and can be performed in contact or even remotely. Such methods are therefore ideally suited to use for the detection of biosignatures, which can be confirmed with supporting instrumentation. Here, we discuss the use of Raman and Fourier Transform Infrared (FT-IR) spectroscopies for the detection and characterization of biosignatures from colonies of the fungus Cryomyces antarcticus, grown on Martian analogues and exposed to increasing doses of UV irradiation under dried conditions. The results report significant UV-induced DNA damage, but the non-exceeding of thresholds for allowing DNA amplification and detection, while the spectral properties of the fungal melanin remained unaltered, and pigment detection and identification was achieved via complementary analytical techniques. Finally, this work found that fungal cell wall compounds, likely chitin, were not degraded, and were still detectable even after high UV irradiation doses. The implications for the preservation and detection of biosignatures in extraterrestrial environments are discussed.

Highlights

The detection of biosignatures on Mars is of outstanding interest in the current field of astrobiology, and drives various fields of research, ranging from new sample collection strategies to the development of more sensitive detection techniques
For each substrate (OS, P-MRS, Sulfatic Mars Regolith Simulant (S-MRS)), we investigated pivotal samples from the EVT2 treatment (i.e., CTRs, 5.5 × 102 kJ/m2, and 5.5 × 105 kJ/m2 samples; Table 1); the C. antarcticus colonies grown under physiological conditions on Malt Extract Agar (MEA) without substrate mixing were used as positive controls (POS CTRs)
We investigated the stability of biomolecules in the black fungus C. antarcticus after exposure to the ground-based simulations performed in preparation for the spaceexposure Biology and Mars Experiment (BIOMEX) project and in support of the biosignature detection method planned for the explorative mission on Mars

Summary

Introduction

The detection of biosignatures on Mars is of outstanding interest in the current field of astrobiology, and drives various fields of research, ranging from new sample collection strategies to the development of more sensitive detection techniques. On Earth, the preservation of organic biosignatures is principally influenced by the rates of biological records production and alterations from biological recycling and abiotic factors (e.g., radiation), the latter of which must not exceed the former. Some types of biosignatures have been found to be more resistant to certain degradation processes, while some environments may be more favorable in preserving some types than others [1,2,3]. Research on these issues is a driving factor in designing explorative strategies for life-detection missions throughout the Solar System. Microorganisms can be found at depths of a few to tens of millimeters in rock interiors; these are so-called cryptoendolithic organisms

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