Icy Moon Oceans May Boil Due to Internal Shifts,New Study Finds
WASHINGTON – Subsurface oceans within icy moons orbiting the outer planets may not be stable features,and could even boil under certain conditions,according to research published today in Nature Astronomy. The study highlights a previously underappreciated result of the density difference between liquid water and ice – approximately 10 percent - and its impact on the internal pressure of these moons.
Scientists have long suspected the existence of oceans beneath the icy shells of moons like Enceladus, based on observed geological activity such as geysers. These oceans are generally believed to be sustained by tidal heating,generated by gravitational interactions with their host planets. However, a new analysis reveals that these interactions aren’t always constant.
The research demonstrates that as an icy moon’s interior melts, it shrinks in volume. This creates an area of low pressure directly beneath the icy shell. For smaller moons, this pressure drop could be significant enough to cause the ocean water to boil.
The stability of these oceans is further complex by the dynamic nature of the outer Solar System. While the current planetary arrangement appears fixed, evidence suggests the outer planets underwent orbital shifts early in their history. Even Earth experiences long-term orbital cycles that influence ice ages. The complex interplay of multiple moons and a giant planet creates a system where gravitational stresses, and thus tidal heating, can fluctuate over time.
This means that subsurface oceans aren’t necessarily permanent fixtures, but may instead experience periods of melting and refreezing.The study challenges the assumption that these oceans are either continuously maintained by constant forces or remnants of the moons’ initial hot formation, suggesting a more cyclical process.
