Institute of Space & Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuou, Sagamihara, Kanagawa 252-5210, Japan.
School of Life Science, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
Life Sci Space Res (Amst). 2022 Aug;34:53-67. doi: 10.1016/j.lssr.2022.07.001. Epub 2022 Jul 9.
The detection and analysis of extraterrestrial life are important issues of space science. Mars is among the most important planets to explore for extraterrestrial life, owing both to its physical properties and to its ancient and present environments as revealed by previous exploration missions. In this paper, we present a comparative study of methods for detecting extraterrestrial life and life-related substances. To this end, we have classified and summarized the characteristics targeted for the detection of extraterrestrial life in solar system exploration mission and the methods used to evaluate them. A summary table is presented. We conclude that at this moment (i) there is no realistic single detection method capable of concluding the discovery of extraterrestrial life, (ii) no single method has an advantage over the others in all respects, and (iii) there is no single method capable of distinguishing extraterrestrial life from terrestrial life. Therefore, a combination of complementary methods is essential. We emphasize the importance of endeavoring to detect extraterrestrial life without overlooking possible alien life forms, even at the cost of tolerating false positives. Summaries of both the targets and the detection methods should be updated continuously, and comparative studies of both should be pursued. Although this study assumes Mars to be a model site for the primary environment for life searches, both the targets and detection methods described herein will also be useful for searching for extraterrestrial life in any celestial environment and for the initial inspection of returned samples.
外星生命的探测和分析是空间科学的重要课题。火星是探索外星生命最重要的行星之一，这既与它的物理特性有关，也与以往探测任务揭示的其古老和现今的环境有关。在本文中，我们对探测外星生命和与生命相关物质的方法进行了比较研究。为此，我们对太阳系探测任务中针对外星生命探测的目标特征及其评估方法进行了分类和总结。并给出了一个总结表。我们得出的结论是：(i) 目前没有一种可行的单一检测方法能够确定外星生命的存在；(ii) 没有一种方法在所有方面都具有优势；(iii) 没有一种方法能够将外星生命与地球生命区分开来。因此，必须结合互补的方法。我们强调，即使需要容忍假阳性，也必须努力探测外星生命，而不能忽视可能的外星生命形式。目标和检测方法的摘要应不断更新，并对它们进行比较研究。虽然本研究假设火星是生命搜索的主要环境的模型地点，但本文所描述的目标和检测方法也将有助于在任何天体环境中寻找外星生命，并对返回样本进行初步检查。
