[B-CG03] Earth and Planetary Science Frontiers for Life and Global Environment

[BCG03-P04] New procedures to inactivate microorganisms for Martian life detection

*Mariko Kouduka¹, Yuri Sueoka¹, Yohey Suzuki¹ (1.Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.)

Keywords:backward planetary protection, rock-hosted microorganisms, viral and bacterial disinfection, anti-scattering agent

For sample return missions from Mars, the risk assessment of putative Martian life (backward planetary protection) represents technological and social challenges. It is aimed to develop procedures for the inactivation of microorganisms such bacteria and viruses without losing the capability of life detection by high-sensitivity analytical measurements. In the present study, near-saturated calcium chloride solution was evaluated for the short-term inactivation of model bacterial and viral organisms. The entrapment of cells in calcium carbonate was also evaluated. Based on cultivation-based assessments, it was revealed that the near-saturated calcium chloride solution inactivated Escherichia coli and Bacteriophage T4 within one minute regardless of subsequent calcium carbonate precipitation. E. coli cells inactivated with the near-saturated calcium chloride solution were found to be entrapped within calcium carbonate precipitates. The entrapped cells were embedded in hydrophilic resin, the E. coli cells were clearly visualized without cell destruction. As the entrapment of microbial cells with CaCO₃ particles has some advantages such as anti-scattering effect and minimizing the analytical inference for organic compounds. Thus, the method developed in this study has the potential to be applied to life detection procedures potentially conducted by rovers and astronauts on Mars. In additions, our procedures are feasible at confinement facilities in space stations and on Earth.