Europa's sinking ice may slowly deliver ingredients for life to its subsurface ocean

A new modeling study by researchers including Austin Green suggests salt-rich patches of Europa's near-surface ice can become denser and weaker, detach, and sink through an approximately 30-kilometer ice shell, carrying oxidants and other chemicals toward the hidden ocean. NASA's Europa Clipper is scheduled to arrive at Jupiter in 2030 and will conduct close flybys to study Europa's ice shell and ocean in greater detail.

A new study proposes a slow geological route for surface materials to reach Europa's subsurface ocean. The work, led by Austin Green (now at Virginia Tech) with contributions from researchers at Washington State University, applies computer models to test whether dense, salt-rich ice near the surface can detach and sink through a thick ice shell. The process is compared to an Earth geological phenomenon and was explored across multiple modeled scenarios. The research was published in The Planetary Science Journal on Jan. 20. Key findings: - Models used an ice shell roughly 30 kilometers (about 18.6 miles) thick and examined six different scenarios. - In all scenarios, surface material within the top roughly 300 meters moved downward toward the base of the shell. - Salt-rich ice can become both denser and mechanically weaker than adjacent purer ice, allowing it to detach and 'drip' downward (a process the authors liken to lithospheric foundering). - Simulated timescales varied: sinking began after as little as about 30,000 years in weakened shells, and in other runs began after 1–3 million years and reached the base after 5–10 million years. - The mechanism could provide a steady pathway for surface-produced oxidants and other chemicals to reach the hidden ocean beneath the ice. Summary: The study offers a potential, gradual mechanism by which surface-produced chemicals on Europa could be transported into its subsurface ocean, addressing a long-standing question about how oxidants might reach an ocean sealed from sunlight. NASA's Europa Clipper mission, arriving in the Jovian system in April 2030 and planning nearly 50 close flybys, will gather data that can help evaluate the ice-shell structure and the plausibility of this transport process.