Survival of Moss Reproductive Structures under Simulated Martian Environmental Conditions and Extreme Thermal Stress: Vibrational Spectroscopic Study and Astrobiological Implications

摘要

The principal goal of astrobiology is the search for extraterrestrial life forms. A key aspect is the study of theability of different kinds of terrestrial organisms to support simulated extraterrestrial environmental conditions.Mosses are multicellular green plants, poorly studied from an astrobiological perspective. In this paper, we reportexperimental results obtained using two species of moss, which demonstrate that both the spores of the mossFunaria hygrometrica as well as the desiccated vegetative gametophyte shoots of the moss Tortella squarrosa(=Pleurochaete squarrosa) were capable of resisting Simulated Martian Environmental Conditions (SMEC): Marssimulated atmospheric composition 99.9% CO2, and 0.6% H2O with a pressure of 7 mbars, -73 ºC and UV irradiationof 30 mW cm-2 in a wavelength range of 200-400 nm under a limited short time of exposition of 2 hours. After beingexposed to SMEC and then transferred to an appropriate growth medium, the F. hygrometrica spores germinated,producing typical gametophyte protonemal cells and leafy shoots. Likewise, detached leaves from SMEC-exposedgametophyte shoots of T. squarrosa retained the ability to produce new protonemata and shoots under suitablegrowth conditions. Furthermore, we studied the tolerance of these moss structures to a thermal stress of 100 °C for 1h; in both cases the spores and shoots were capable of resisting this heat treatment. Our study using FT-Raman andFT-IR vibrational spectroscopy demonstrated that neither spores nor shoots apparently suffered significant damagein their biomolecular makeup after being subject to these stress treatments. The implications of these findings for thesearch of life on Mars are discussed.