Prometheus: An Io Plume Sample Return Concept

Volcanic plumes on Io have been observed during every spacecraft encounter from Voyager to Juno. The material within the plume ejecta provides direct insight into Io’s composition in the form of volcanic gases and pyroclastic grains. Return of these ejecta materials would provide a window into Io’s origins and would represent the next logical step in sample return, and in the exploration of the Jupiter system. The Prometheus Io Sample Return mission concept proposes to collect a plume sample, supported by remote observations to provide scientific context. The Prometheus mission concept can be tailored to either a Discovery or New Frontiers scope, informed by both the Visions and Voyages (V&V) and Origins, Worlds, and Life (OWL) Decadal Surveys. In particular, it responds to the New Frontiers 5 objectives for an Io Observer mission. Additional science from the returned sample would address important questions related to the formation of the Solar System and Jupiter’s circumplanetary disk. To accomplish these objectives, the sample collection system (SCS) draws on the aerogel designs of Stardust and the Genesis sampling plates made of pure materials. A suite of remote sensing instruments supports the targeting and contextualization of plume samples. To safely collect the sample, the spacecraft must be capable of surviving the challenging radiation environment inside of Callisto’s orbit as well as the micrometeoroid and orbital debris (MMOD) environment when sampling Io’s plumes. These obstacles are overcome by applying flight-proven technologies from missions operating in similar environments: Juno, Europa Clipper, and Stardust. The flight system selected for the mission concept is a solar-powered Lucylike spacecraft bus with Stardust-like sample return capsule (SRC) which houses and deploys the SCS. Ram-facing Whipple shields protect the solar arrays and payload from the particles in the plume and a radiation vault protects spacecraft compute elements from Jupiter’s strong radiation environment. In this paper we first address the science rationale for the Prometheus mission and how this feeds into mission goals and objectives. We next describe a potential science payload alongside a concept of operations. We summarize the technical details of the mission concept and architectural options. Two trajectory options are discussed, one synergistically combining sample collection and complementary remote science and the other prioritizing the sample collection. Finally, the details of the baseline of the flight system and design trades are described.