Abstract EANA2026-241

Enceladus is widely regarded as one of the most promising targets in the Solar System in the search for extraterrestrial life. Measurements by the Cassini mission revealed that its cryovolcanic plumes contain sodium-bearing salts, silica nanoparticles indicative of hydrothermal water-rock interactions, molecular hydrogen, complex organic compounds, and phosphates, providing compelling evidence for a global subsurface ocean that may offer habitable conditions.

While plume fly-through missions directly sample freshly ejected ocean material, future landed missions offer the opportunity to investigate deposits formed by repeated plume fallout. These deposits have been identified as one of the most accessible astrobiological targets on Enceladus because they provide direct access to ocean-derived material without penetrating the global ice shell. Numerical models predict that a significant fraction of the solid plume particles is redeposited around the south polar terrain, producing locally enhanced accumulation rates. We therefore hypothesize that the shallow subsurface forms a vertically stratified archive of plume deposition. Access to only the upper few meters may reveal temporal variations in plume activity, ocean chemistry and depositional processes while sampling material that potentially represents thousands to tens of thousands of years of accumulation, depending on local deposition rates, porosity, compaction and surface reworking.

To support future ESA L4 mission studies, this work presents a system-level trade study of candidate architectures for accessing this shallow subsurface archive. Nine concepts are evaluated, including ballistic penetrators, hybrid impact systems, anchored dynamic hammering probes, conventional drill-string systems, anchored rotary coring drills, thermally assisted rotary coring drills, and electrically and chemically powered cryobots. A morphological analysis combined with a weighted decision matrix compares the concepts with respect to scientific return, preservation of stratigraphic context, penetration capability, sample integrity, energy demand, operational flexibility, mechanical complexity, technology readiness and mission risk.

A complementary payload architecture is proposed for both in-situ characterization and laboratory analysis of returned samples. The penetration system incorporates temperature sensing, penetration resistance measurements, electrical conductivity and permittivity sensors, microscopic imaging, near-infrared spectroscopy and Raman spectroscopy for continuous depth-resolved profiling. Returned samples are subsequently analysed within the lander using complementary high-information-content techniques, including gas chromatography–mass spectrometry, laser desorption mass spectrometry, evolved gas analysis, microfluidic wet chemistry and high-resolution microscopy.

The presented framework integrates astrobiological science objectives with systems engineering and provides a technology-neutral methodology for selecting future shallow subsurface access systems for Enceladus.