[M-IS06] Astrobiology

[MIS06-P07] A research plan to revisit the sterilization efficiency of microbes during hypervelocity impacts

*Kosuke Kurosawa¹, Shunta Kimura², Shino Suzuki², Kazuhisa Fujita², Haruka Oono¹, Takaya Okamoto¹, Takafumi Matsui¹ (1.Planetary Exploration Research Center, Chiba Institute of Technology, 2.JAXA)

The transport process of life originating in planetary bodies to the other body moving through space has been studied for a long time. The idea that the Earth’s life was brought to the Earth by such transport is called the Panspermia hypothesis. Hypervelocity impacts are considered to be a driving force pertaining to the Panspermia, because it can accelerate the surface materials to the velocity higher than the escape velocity of the body smaller than Mars. In recent years, such considerations have also become important in the context of planetary protection and quarantine. In the Mars–Phobos–Deimos system, the surface materials on Mars are deposited on Martian satellites, indicating that the MMX space craft is likely to bring back Martian rocks from Mars in addition to regolith from Phobos. Since the possibility that some kind of microbes have lived on Mars cannot be ruled out by the current scientific knowledge, it is possible that the samples brought back from the Martian satellites may contain a trace amount of microbes originating on Mars. This is called the planetary quarantine issue, and it is necessary to evaluate the safety of the samples prior to the Earth return.
Even if there are microbes encapsulated in rocky media, it is not obvious whether the microbe can survive the pressure and temperature increases caused by intense deformation with extremely high strain rate during hypervelocity impacts. In order to investigate the feasibility of the panspermia hypothesis or the survival rate during the transfer of materials from Mars to its satellites, over 10 experiments have been conducted to investigate the survival rate of microbes. However, we were wondering that there are many problems in previous experiments, such as the limited number of data due to the difficulty of the experiment and unrealistic experimental conditions. Therefore, we have started to establish an experimental system and method to efficiently to obtain the data while keeping the experimental conditions close to the real ones. In the presentation, we will report on the current status of the experimental system.