Formation of oceans within icy moons could cause the waters to boil

"Our explanation of the outer Solar System has revealed a host of icy moons, many with surface features that suggest a complex geology. In some cases, these features-most notably the geysers of Enceladus-hint at the presence of oceans beneath the icy surfaces. These oceans have been ascribed to gravitational interactions that cause flexing and friction within the moon, creating enough heat to melt the body's interior."

"A new study, released today by Nature Astronomy, looks at one of the consequences of the difference in density between liquid water and ice (about 10 percent): the potential for the moon's interior to shrink as it melts, leaving an area of low pressure immediately below its icy shell. If the moon is small enough, this study suggests, that could cause the surface of the ocean to boil."

Icy moons can develop subsurface oceans when gravitational interactions produce tidal flexing and friction that melt their interiors. Orbital interactions are often cyclical, so tidal heating can vary over time, causing oceans to form, refreeze, or disappear. Because liquid water is about ten percent denser than ice, melting can produce interior volume loss and create a low-pressure region immediately beneath the icy shell. In sufficiently small moons, that low pressure can allow the subsurface water to boil. Surface features such as geysers provide evidence that these dynamic processes are active on some moons.

Read at Ars Technica