Wdowiak T J, Gerakines P A, Agresti D G, Clemett S J
Department of Physics, University of Alabama at Birmingham, Birmingham, AL, USA.
Astrobiology. 2001 Winter;1(4):467-76. doi: 10.1089/153110701753593865.
If Europa is to be of primary exobiological interest, namely, as a habitat for extant life, it is obvious that (a) a hydrosphere must prevail beneath the cryosphere for a long time, (b) internal energy sources must be present in a sufficient state of activity, and (c) a reasonable technical means must be available for assessing if indeed life does exist in the hypothesized hydrosphere. This discussion focuses on the last point, namely, technological issues, because the trend of the compounding evidence about Europa indicates that the first two points are likely to be true. First, we present a consideration of time-of-flight mass spectroscopy conducted in situ on the cryosphere surface of Europa during a first landed robotic mission. We assert that this is a reasonable technical means not only for exploring the composition of the cryosphere itself, but also for locating any biomolecular indicators of extant life brought to the surface through cryosphere activity. Secondly, this work also addresses practical issues inherent in any kind of instrumental interrogation of a surface whose properties are governed by radiation chemistry. This includes advocating the construction of a Europan surface simulator to familiarize instrumental system developers with the spacecraft- and instrument-scale conditions under which such an interrogation would take place on Europa. Such a simulator is mandatory in certification of the functional utility of a flight instrument.
如果木卫二要成为主要的外星生物学研究对象，即作为现存生命的栖息地，那么显然：（a）水圈必须在冰冻圈之下长期存在；（b）内部能源必须处于足够活跃的状态；（c）必须有合理的技术手段来评估假设的水圈中是否确实存在生命。本讨论聚焦于最后一点，即技术问题，因为有关木卫二的综合证据趋势表明前两点可能是成立的。首先，我们探讨在首次着陆的机器人任务期间对木卫二冰冻圈表面进行原位飞行时间质谱分析的情况。我们认为这不仅是探索冰冻圈本身成分的合理技术手段，也是寻找通过冰冻圈活动带到表面的现存生命的任何生物分子指标的合理技术手段。其次，这项工作还涉及对受辐射化学影响其性质的表面进行任何仪器探测所固有的实际问题。这包括主张建造一个木卫二表面模拟器，以使仪器系统开发者熟悉在木卫二上进行此类探测时航天器和仪器规模的条件。这样的模拟器对于飞行仪器功能效用的认证是必不可少的。
