Microbial Setups for Hypervelocity Impact Sterilization Tests

Abstract The Japan Aerospace Exploration Agency (JAXA) plans to conduct the Martian Moon Exploration (MMX) mission, which aims to return samples from Phobos. Estimation of the potential microbial abundance on Phobos is crucial for the MMX mission in terms of planetary protection. Microorganisms might have been transported from Mars by meteorite impacts on Mars and subsequent transfer with Mars’s rocks and sand to Phobos. Therefore, the assessment of hypervelocity impact sterilization rates at the time of landing on the Phobos surface is required to estimate the potential surviving-microorganism density on Phobos surface. In order to evaluate the hypervelocity impact sterilization rates, impact tests were conducted using a light-gas gun in JAXA, to simulate the landing process on the Phobos surface. In this study, experimental handling of microorganisms was examined. We established the methods to distinguish the test microorganisms from contaminated bacteria from environment, methods to load cells or phages in a sample well of a basalt projectile and methods to count living bacterial cells in target sand. We have constructed an experimental setup for each of the experimental steps to conduct the hypervelocity impact tests for four different microorganisms.