Enceladus is unique as an astrobiology target in that it hosts an active plume sourced directly from its habitable subsurface ocean. Ice particles from the plume contain geochemical constituents that are diagnostic of the ocean conditions, and may hold traces of life and/or biosignatures, if they exist. Up to 93% of the plume particles fall back onto the surface of Enceladus. The low radiation environment and present-day activity are favorable to the preservation of any complex organics and putative biosignatures contained within these particles. Laboratory experiments and modeling suggest that plume deposits would likely be weakly consolidated and relatively easy to sample. Sampling systems like a dual rasp, under development to achieve technology readiness level (TRL) 5 in 2021, would enable a landed mission on Enceladus’ surface to acquire large amounts of surface materials, a requirement for analysis of trace constituents. A landed mission on Enceladus could greatly enhance our understanding of the chemical makeup of plume particles and the subsurface ocean, and seek traces of life and/or biosignatures.

土卫二作为天体生物学目标是独一无二的，因为它拥有直接来自可居住的地下海洋的活跃羽流。羽流中的冰颗粒含有可诊断海洋状况的地球化学成分，如果存在的话，可能带有生命痕迹和/或生物特征。多达 93% 的羽流颗粒会落回土卫二的表面。低辐射环境和当今的活动有利于保存这些粒子中包含的任何复杂有机物和假定的生物特征。实验室实验和建模表明，羽状沉积物可能是弱固结的并且相对容易采样。采样系统如双锉刀，正在开发中，以在 2021 年达到技术准备水平 (TRL) 5，将使土卫二表面的着陆任务能够获取大量表面材料，这是分析微量成分的要求。土卫二的着陆任务可以极大地增强我们对羽状粒子和地下海洋化学组成的理解，并寻找生命和/或生物特征的踪迹。