Feasibility of a Mission to Enceladus' Subsurface Ocean for the Next Planetary Science Decadal Survey

Saturn's moon Enceladus is a high priority target for astrobiology as it harbors a subsurface ocean that erupts into space and is likely habitable. Searching for life at Enceladus is a top priority, near term goal of Ocean Worlds exploration (e.g., Hendrix et al., 2019, The NASA Roadmap to Ocean Worlds, and references therein). Several mission concepts to search for life in Enceladus' plume have been studied including proposed Discovery and New Frontiers missions. Is a mission that accesses the ocean and directly searches for life in unaltered ocean samples feasible in the coming decade? We present the results of an internal study at the Jet Propulsion Laboratory for an ambitious yet implementable mission concept to Enceladus' ocean. This innovative mission would include autonomous landing at Enceladus' south pole and penetration through the ice shell via both an intelligent melt probe and an adaptable multi-terrain robot (robotic eel) that navigates down an erupting vent. Both the eel and melt probe would be instrumented, able to search for evidence of life in samples acquired during their descent, and capable of maneuvering within the ocean. The baseline mission architecture would include a solar-powered orbiter to identify safe, compelling landing zones and relay data to Earth as well as an RTG-powered lander that would execute a precision landing, deploy the melt and eel probes, relay data to the orbiter, and also search for evidence of life in samples of surface material. A new surface sampling system has been developed to enable the latter search, based on experimentally-derived surface strength expectations (Hodyss et al., this meeting). The mission design would not be inhibited by winter darkness at Enceladus' south pole; all operations could be accomplished at any Enceladus season. The concept would utilize the state-of-the-art in astrodynamics techniques, systems architecture, optimization, and advanced manufacturing. A single Flagship-level mission that would search for life on Enceladus' surface, within its ice shell, and in the subsurface ocean may be the most comprehensive opportunity for astrobiology in the coming decade.