title: Preservation of Biomarkers from Cyanobacteria Mixed with Mars-Like Regolith Under Simulated Martian Atmosphere and UV Flux.
abstract: The space mission EXPOSE-R2 launched on the 24th of July 2014 to the International Space Station is carrying the BIOMEX (BIOlogy and Mars EXperiment) experiment aimed at investigating the endurance of extremophiles and stability of biomolecules under space and Mars-like conditions. In order to prepare the analyses of the returned samples, ground-based simulations were carried out in Planetary and Space Simulation facilities. During the ground-based simulations, Chroococcidiopsis cells mixed with two Martian mineral analogues (phyllosilicatic and sulfatic Mars regolith simulants) were exposed to a Martian simulated atmosphere combined or not with UV irradiation corresponding to the dose received during a 1-year-exposure in low Earth orbit (or half a Martian year on Mars). Cell survival and preservation of potential biomarkers such as photosynthetic and photoprotective pigments or DNA were assessed by colony forming ability assays, confocal laser scanning microscopy, Raman spectroscopy and PCR-based assays. DNA and photoprotective pigments (carotenoids) were detectable after simulations of the space mission (570 MJ/m(2) of UV 200-400 nm irradiation and Martian simulated atmosphere), even though signals were attenuated by the treatment. The fluorescence signal from photosynthetic pigments was differently preserved after UV irradiation, depending on the thickness of the samples. UV irradiation caused a high background fluorescence of the Martian mineral analogues, as revealed by Raman spectroscopy. Further investigation will be needed to ensure unambiguous identification and operations of future Mars missions. However, a 3-month exposure to a Martian simulated atmosphere showed no significant damaging effect on the tested cyanobacterial biosignatures, pointing out the relevance of the latter for future investigations after the EXPOSE-R2 mission. Data gathered during the ground-based simulations will contribute to interpret results from space experiments and guide our search for life on Mars.
authors.affiliation: Department of Biology, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Mickael
authors.initials: M
authors.lastname: Baqué
authors.affiliation: Department of Biology, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Cyprien
authors.initials: C
authors.lastname: Verseux
authors.affiliation: German Aerospace Center (DLR), Institute of Planetary Research, Berlin, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Böttger
authors.affiliation: Radiation Biology Department, German Aerospace Center (DLR), Institute of Aerospace Medicine, Köln, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Rabbow
authors.affiliation: German Aerospace Center (DLR), Institute of Planetary Research, Berlin, Germany.
authors.forename: Jean-Pierre Paul
authors.initials: JP
authors.lastname: de Vera
authors.affiliation: Department of Biology, University of Rome Tor Vergata, Rome, Italy. billi@uniroma2.it.|Dipartimento di Biologia, Università di Roma "Tor Vergata", Rome, Italy. billi@uniroma2.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Billi
mesh_terms: D001272:Atmosphere / Q000032:analysis*; D000458:Cyanobacteria / Q000502:physiology / Q000528:radiation effects*; D004269:DNA, Bacterial / Q000235:genetics; D018534:Earth, Planet; D018559:Exobiology; D005118:Extraterrestrial Environment; D006801:Humans; D018535:Mars; D010788:Photosynthesis / Q000528:radiation effects*; D018561:Space Simulation; D018531:Spacecraft; D013171:Spores, Bacterial / Q000502:physiology / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial
keywords: Astrobiology; Biosignatures; Cyanobacteria; EXPOSE-R2; Martian regoliths