Limits of life at spaceflight conditions: survival of lichens to simulated microgravity

The search for extraterrestrial life and finding habitable environments on other planets and satellites like Mars, Europa, Enceladus and Titan are a priority of NASA and ESA, since the last decade. To contribute to these highly significant challenges, research has been done with established exposure platforms like those on the Foton satellite and EXPOSE on the ISS expanding now to ESA’s platform Bartolomeo. These were used to expose samples to space vacuum and space radiation, but also to provide gas supply and selected planetary radiation environments. Results obtained by these experiments have allowed to get supplemental knowledge necessary for supporting future investigations to search for life in the universe.

Several extremophile lichen species, have been exposed to extraterrestrial environments, i.e. space- and Mars like parameters, during short and long periods on board of ESA’s space missions (Foton M2 and M3, EXPOSE E and R2) to investigate the limits of terrestrial life. To maximize the scientific outcome of these experiments, LICHENS [1], LITHOPANSPERMIA [2], LIFE [3], and BIOMEX [4], a common elaboration and analysis of the results obtained on analogue field studies with results obtained in planetary simulation facilities was necessary to check the survival potential and vitality of the samples before flight. Tests and experiments at different simulation facilities at DLR, and at INTA, included the exposure to space vacuum, space UV radiation and space cosmic radiation, and to Mars-like environment, i.e. Mars atmospheric composition and pressure, as well as Mars UV radiation. Not microgravity or reduced gravity, which is present in space and on Mars, was tried.

Here we show the results of the resistance of two extremophile vagrant lichen species, Xanthoparmelia hueana and Circinaria gyrosa, to simulated microgravity (rotation speed of clinostate: 1 rpm) using the UNZIP clinostate at CIB-CSIC (Centro Investigaciones Biológicas Margarita Salas). This is the first time that lichens will be exposed to weightlessness environment in an attempt to isolate the potential contribution of microgravity from other extraterrestrial factors (radiation, vacuum). Combinations of simulated spaceflight conditions, including microgravity, will be necessary to check how this parameter affects the biomolecular level of lichens and their microbiome.

 

References

[1] Sancho, L.G., de la Torre, R., Horneck, G., Ascaso, C., de los Rios, A., Pintado, A., and Schuster, M. (2007) Lichens survive in space: results from the 2005 LICHENS experiment. Astrobiology 7:443–454. https://doi.org/10.1089/ast.2006.0046

[2] de la Torre, R., Sancho, L.G., Horneck, G., de los Ríos, A., Wierzchos, J., Olsson-Francis, K., and Ott, S. (2010) Survival of lichens and bacteria exposed to outer space conditions—results of the Lithopanspermia experiments. Icarus 208:735–748. https://doi.org/10.1016/j.icarus.2010.03.010

[3] Onofri, S., de la Torre, R., de Vera, J.P., Ott, S., Zucconi, L., Selbmann, L., Scalzi, G., Venkateswaran, K.J., Rabbow, E., Sánchez, F.J., and Horneck, G. (2012) Survival of rock-colonizing organisms after 1.5 year in outer space. Astrobiology 12: 508-516. https://doi.org/10.1089/ast.2011.0736

[4] de Vera, J.P., , and the BIOMEX-Team and associatesTeam (Ute Boettger, Rosa de la Torre Noetzel et al.) (2019) Limits of Life and the Habitability of Mars: The ESA Space Experiment BIOMEX on the ISS. Astrobiology, 19-2. https://doi.org/10.1089/ast.2018.1897.