2026-01-15 ワシントン州立大学（WSU）
＜関連情報＞
- https://news.wsu.edu/press-release/2026/01/15/study-suggests-pathway-for-life-in-europas-ocean/
- https://iopscience.iop.org/article/10.3847/PSJ/ae2b6f
滴り落ちる破壊：エウロパの氷殻における塩分駆動による粘性表面収束の探査 Dripping to Destruction: Exploring Salt-driven Viscous Surface Convergence in Europa’s Icy Shell
A. P. Green and C. M. Cooper
The Planetary Science Journal Published: 2026 January 20
DOI:10.3847/PSJ/ae2b6f
Abstract
The Europan ice shell is thought to be simultaneously a key contributor and a barrier to the underlying ocean’s habitability. Life-supporting oxidants formed by surface radiolysis have the potential to be a significant component toward the long-term sustenance of a Europan biosphere. However, these oxidants must first be transported through the ice shell to its base in order to be accessible by Europa’s ocean. We propose that a viscous lithospheric foundering process (“dripping”) driven by densification and weakening in salt-rich surface ice may provide a pathway for these surface oxidants to reach the ocean. We find that a viscous dripping process is capable of cycling surface ice to the base of the shell, transporting it in 3 Myr or less, depending on the level of salt-driven lithospheric weakening. Lithospheric drips can accommodate tens of kilometers of surface convergence within the salt-enriched region of the shell. We discover that the surrounding salt-poor ice locks the boundaries of the dripping region in place, encouraging lithospheric thinning and extension. We conclude that this dripping process is a viable avenue toward providing the mechanism for surface ice transport that could support Europan ocean habitability, but more work is needed to fully understand how the presence of saline ice affects ice shell deformation and dynamic behavior.
