Data returned from the Cassini–Huygens mission have strengthened Enceladus, a small icy moon of Saturn, as an important target in the search for life in our solar system. Information gathered from Cassini to support this includes the presence of a subsurface liquid water ocean, vapor plumes and ice grains emanating from its south polar region, and the detection of essential elements and organic material that could potentially support life. However, several outstanding questions remain regarding the connectivity of plume material to the ocean and the composition of the complex organic material. Herein we introduce Tiger, a mission concept developed during the 2020 Planetary Science Summer School at NASA’s Jet Propulsion Laboratory. Tiger is a flyby mission that would help further constrain the habitability of Enceladus through two science objectives: (1) determine whether Enceladus’s volatile inventory undergoes synthesis of complex organic species that are evidence for a habitable ocean, and (2) determine whether Enceladus’s plume material is supplied directly from the ocean or if it interfaces with other reservoirs within the ice shell. To address the science goals in a total of eight flybys, Tiger would carry a four-instrument payload, including a mass spectrometer, a single-band ice-penetrating radar, an ultraviolet imaging spectrograph, and an imaging camera. We discuss Tiger's instrument and mission architecture, as well as the trades and challenges associated with a habitability-focused New Frontiers–class flyby mission to Enceladus.
Enceladus is an icy world with potentially habitable conditions, as suggested by the coincident presence of a subsurface ocean, an active energy source due to water-rock interactions, and the basic chemical ingredients necessary for terrestrial life. Among all ocean worlds in our Solar System, Enceladus is the only active body that provides direct access to its ocean through the ongoing expulsion of subsurface material from erupting plumes. Here we present the Enceladus Touchdown aNalyzing Astrobiology (ETNA) mission, a concept designed during the 2019 Caltech Space Challenge. ETNA’s goals are to determine whether Enceladus provides habitable conditions and what (pre-) biotic signatures characterize Enceladus. ETNA would sample and analyze expelled plume materials at the South Polar Terrain (SPT) during plume fly-throughs and landed operations. An orbiter includes an ultraviolet imaging spectrometer, an optical camera, and radio science and a landed laboratory includes an ion microscope and mass spectrometer suite, temperature sensors, and an optical camera, plus three seismic geophones deployed during landing. The nominal mission timeline is 2 years in the Saturnian system and ∼1 year in Enceladus orbit with landed operations. The detailed exploration of Enceladus’ plumes and SPT would achieve broad and transformational Solar System science related to the building of habitable worlds and the presence of life elsewhere. The nature of such a mission is particularly timely and relevant given the recently released Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023–2032, which includes a priority recommendation for the dedicated exploration of Enceladus and its habitable potential.
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