Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA.
Astrobiology. 2023 Aug;23(8):862-879. doi: 10.1089/ast.2022.0048.
The Mars 2020 Perseverance rover is equipped with a Sample Caching System (SCS) designed to collect and cache martian core and regolith samples for potential return to Earth. To ensure the integrity of these samples, the mission requirements for each encapsulated sample for return is less than one Earth-sourced viable organism (VO) and more than a 99.9% probability of being free of any Earth-sourced VO. To satisfy the stringent biological contamination requirements in support of return sample science investigations, special bioburden mitigation and reduction approaches were developed and implemented for SCS hardware that would directly contact or be in close proximity to the martian samples. In this study, we describe the implemented approaches for microbiological contamination reduction and mitigation, detail the processes of the SCS aseptic assembly, and report the estimated VO for each returned sample. We found that our conservative estimate of the computed probability of a single VO in the returned sample is more than one order of magnitude lower than the biological contamination requirement while the best estimate exceeds two orders of magnitude.
毅力号火星车配备了一个样本缓存系统（SCS），旨在收集和缓存火星核心和风化层样本，以备将来返回地球。为了确保这些样本的完整性，返回的每个封装样本的任务要求是携带的地球源微生物（VO）少于一个，且有超过 99.9%的概率不含任何地球源 VO。为了满足严格的生物污染要求，以支持返回样本的科学研究，专门制定并实施了特殊的生物负荷减轻和降低措施，用于将直接接触或靠近火星样本的 SCS 硬件。在这项研究中，我们描述了实施的微生物污染减少和减轻的方法，详细说明了 SCS 无菌组装的过程，并报告了每个返回样本的估计 VO。我们发现，我们对返回样本中单个 VO 的计算概率的保守估计比生物污染要求低一个数量级以上，而最佳估计值则超过两个数量级。
