Investigating cryobot performance in realistic ice environments with the Cryotwin

Ice-melting probes, also called cryobots, are envisioned as a key technology for accessing the subglacial oceans of icy moons, such as Europa and Enceladus, to search for life. These extraterrestrial ice shells, several kilometers thick, are anticipated to include a dense ice layer transitioning to a porous, mushy zone at the ice-water interface, resembling Earth’s sea ice. Despite this, most terrestrial field tests of cryobots have been conducted in glacial ice, which differs significantly from sea ice in structure and composition. However, for mission planning both types of ice need to be considered.

Digital twins and virtual testbeds can be used for the integration of data and forward simulations for design and decision support subjected to the performance of the cryobot. In this contribution, we extend the functionality of the Cryotwin, an in-house digital twin for cryobots [1,2], to assess the influence of porosity on the cryobot’s performance. Our simulation model predicts the cryobot’s melting velocity, efficiency and transit time [3] for the unique thermal and porosity gradients encountered in sea ice. Mimicking a virtual testbed, our model considers an explicit update of the local environment, comprised of porosity, thermal conductivity, heat capacity, and density, while the cryobot moves downward melting into the ice. Porosity will be incorporated into the simulations based on temperature and salinity measurements from sea ice cores. We take salinity and temperature data from the RESICE database [4], which currently provides data from 287 sea ice cores originating from different geospatial locations and seasons, and feed environmental data into the digital twin’s testbed. Further, we use this data to derive the material properties of the local cryo-environment used in the simulation.

This work provides insights into the operation of future cryobots in extraterrestrial environments that comprise both dense and porous ice. With this study, we want to investigate the importance of analogue testing in sea ice, and demonstrate the value add of comprehensive virtualized digital twin infrastructure, to enhance mission readiness for icy moon exploration.

References:

[1] Kowalski et al., Cryotwin – Digital infrastructure for virtually-assisted preparation and analysis of cryo-robotic exploration missions, 84th EAGE Annual Conference & Exhibition (2023) 1 – 5, doi: 10.3997/2214-4609.2023101223.

[2] Bhattacharya et al., Cryotwin: Toward the Integration of a Predictive Framework for Thermal Drilling, ECCOMAS (2024), doi: 10.23967/eccomas.2024.070

[3] Boxberg et al., Ice Transit and Performance Analysis for Cryorobotic Subglacial Access Missions on Earth and Europa, Astrobiology 23 (2023) 1135-1152, doi: 10.1089/ast.2021.007.

[4] Simson et al., RESICE - Reusability-targeted Enriched Sea Ice Core Database - General Information, Zenodo (2024), doi: 10.5281/zenodo.10866347.