New research suggests that some of the solar system's smallest icy moons may harbor oceans that occasionally boil beneath their frozen shells. The study, published in Nature Astronomy on November 24, provides new insights into how features such as ridges, cliffs, and "tiger stripes" may form on these distant worlds.
Unlike Earth, where geology is driven by molten rock, icy moons like Saturn's Mimas and Enceladus, or Uranus' Miranda, are shaped by the movement of water and ice. Heating from tidal forces exerted by their host planets can cause ice shells to melt or thicken. When ice melts from the bottom, pressure drops, potentially allowing water to reach its triple point, where ice, liquid, and vapor coexist, essentially boiling beneath the surface.
"This process could explain distinctive surface features on small moons that otherwise appear geologically dead," says Max Rudolph, lead author and associate professor of earth and planetary sciences at UC Davis. On larger moons like Titania, however, the ice shell would crack before boiling occurs, leading to different surface formations.