Europa is the closest and probably the most promising target to search for extant life in the Solar System, based on complementary evidence that it may fulfil the key criteria for habitability: the Galileo discovery of a sub-surface ocean; the many indications that the ice shell is active and may be partly permeable to transfer of chemical species, biomolecules and elementary forms of life; the identification of candidate thermal and chemical energy sources necessary to drive a metabolic activity near the ocean floor. In this article we are proposing that ESA collaborates with NASA to design and fly jointly an ambitious and exciting planetary mission, which we call the Joint Europa Mission (JEM), to reach two objectives: perform a full characterization of Europa's habitability with the capabilities of a Europa orbiter, and search for bio-signatures in the environment of Europa (surface, subsurface and exosphere) by the combination of an orbiter and a lander. JEM can build on the advanced understanding of this system which the missions preceding JEM will provide: Juno, JUICE and Europa Clipper, and on the Europa lander concept currently designed by NASA (Maize, report to OPAG, 2019).

中文翻译：

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木卫二联合任务 (JEM) 对木卫二进行多尺度研究，以描述其宜居性和寻找现存生命

欧罗巴是在太阳系中寻找现存生命的最接近，也可能是最有希望的目标，基于补充证据表明它可能满足宜居性的关键标准：伽利略发现了一个次表层海洋；许多迹象表明冰壳是活跃的，并且可能部分渗透化学物种、生物分子和基本生命形式；确定推动海底附近代谢活动所需的候选热能和化学能源。在本文中，我们提议 ESA 与 NASA 合作，共同设计和飞行一项雄心勃勃且令人兴奋的行星任务，我们将其称为联合木卫二任务 (JEM)，以实现两个目标：利用以下能力对木卫二的宜居性进行全面表征欧罗巴轨道飞行器，并通过轨道器和着陆器的组合在木卫二的环境（地表、地下和外层）中寻找生物特征。JEM 可以建立在对 JEM 之前的任务（朱诺号、JUICE 和欧罗巴快船）以及目前由 NASA 设计的欧罗巴着陆器概念（Maize，向 OPAG 的报告，2019 年）提供的对该系统的深入理解之上。