Predicting the intrusion depth of a lander on the surface of Enceladus using a regolith stratification model

Saturn’s icy moon Enceladus is the prime target for ESA’s fourth large-class mission (L4) [1]. In addition to placing an orbiter around Enceladus, the mission would involve deploying a lander to the South Polar Terrain of the moon. A crucial parameter to ensure safe landing is the intrusion depth of the lander on Enceladus’ icy surface. In this study, our main goal is to calculate this intrusion depth considering the structure of the ice shell of Enceladus. For this, we use an existing stratification model for granular matter [2,3], where the density of the surface layers increases with depth due to the gravity of Enceladus. We use parameters derived from compression curves of granular ice from laboratory experiments [e.g., 4], such as the turnover pressure and logarithmic transition width from loose to dense packing, as input parameters for the stratification model. Once the stratification of Enceladus’ icy surface is calculated, we predict the intrusion depth of an object (i.e., ESA’s L4 lander) resting on the surface, which compacts the porous, granular ice due to its weight. We will analyze the sensitivity of the calculated intrusion depth on the input parameters and define worst-case scenarios. Moreover, we will consider additional physical processes such as sintering [5] and will discuss next steps involving dynamic compaction.

References:

[1] Helbert et al. (2025) EPSC-DPS2025-1307. [2] Blum et al. (in revision), submitted to A&A. [3] Bürger et al. (2024), JGR: Planets, 129, e2023JE008152. [4] Lorek et al. (2016), A&A 587, A128. [5] Gundlach et al. (2018), MNRAS 479, 5272–5287.