SEAFARER: Navigating Unknown Seas An L4-class space mission concept for the exploration of the Saturnian System developed during the ESA 2024 Summer School Alpbach

The Saturnian System hosts a wide diversity of planetary environments, from an active ocean world to the only moon in our Solar System with a dense atmosphere and complex chemistry. These worlds are natural laboratories to test planetary evolution and the geophysical and chemical processes that shape Habitability. We present an L4-class space mission concept developed by a team of European students during the European Space Agency (ESA) Summer School Alpbach 2024 with the objective of exploring the range of possible Habitability scenarios on a single system of moons. The proposed space mission concept, SEAFARER - Surveying Environments Across the Saturnian System For hAbitability REseaRch, will have dedicated mission phases to Enceladus and Titan, allowing the exploration of different rich geochemical settings within the same space mission.  

The SEAFARER space mission consists of three specialised segments: an orbiter, a Saturn atmospheric entry probe and a planetary lander to be deployed on Kraken Mare, Titan’s largest hydrocarbon sea. The orbiter will survey the Saturnian System using a remote sensing suite, performing multiple flybys of Saturn and its moons, with close flybys of Mimas and Enceladus. During its trajectory, SEAFARER will analyse the dust environment, while monitoring the long term weather on Saturn and ring dynamics. The orbiter will investigate Mimas for the presence of a possible young subsurface ocean through a series of flybys. Following this phase, SEAFARER will raise its periapsis, conducting a series of targeted flybys of Enceladus. During these, it will sample and analyse material from the Enceladus’s south polar plume, searching for organic chemistry and test the possibility of hydrothermal activity and evidence for a biosphere. The mission will reach the final phase entering a high-inclination orbit around Titan. The orbiter will monitor the dense atmosphere of Titan including its dynamics (polar vortex, superrotation), hazes (formation, chemistry), tracking its seasonal evolution from polar to equatorial latitudes. Titan’s  surface will be mapped via radar, enabling for tracking the hydrological cycle and surface processes, such as cryovolcanism. 

The atmospheric probe will be deployed as SEAFARER entry the Saturn System. It will perform in situ studies of composition and dynamics on the Saturn’s upper atmosphere, providing insight into Saturn formation and orbital evolution, constraining planetary migration scenarios that resulted in the present-day Solar System architecture. 

The Titan lander will be deployed from a high-inclination orbit on Kraken Mare, providing the first oceanographic mission outside the Earth. The lander will act as a drifter, measuring sea currents, physical parameters such as surface temperature and sea-atmosphere energy fluxes, while providing weather information on variables such as precipitation. This mission’s segment will provide a unique insight into the hydrocarbon sea as a reservoir for the methane-based hydrological cycle. 

SEAFARER is expected to address the Saturnian System planetary science questions stemming from the legacy of the NASA/ESA/Cassini-Huygens mission. SEAFARER instrument suite will provide remote sensing and in situ measurements of a diversity of Ocean Worlds, from the possible young Mimas to the active Enceladus where complex organic chemistry can be studied. SEAFARER will determine whether Enceladus hosts a biosphere. The mission will explore the complexity of a methane-rich atmosphere and its hazes with implications for radiative transfer studies and global climate models. SEAFARER Titan lander will provide the first in situ exploration of a sea outside the Earth, rendering it a true oceanographic mission in the outer Solar System.