Question

A planetary satellite orbiting a gas giant exhibits a liquid water ocean beneath a solid ice shell. Three scientists propose different models to explain the source of the thermal energy that prevents the subsurface ocean from freezing.

Scientist 1
The primary source of heat is tidal dissipation. As the satellite follows an eccentric orbit, the gravitational pull of the gas giant causes periodic deformation (flexing) of the satellite's silicate mantle and metallic core. This friction generates tidal heat at a rate of approximately $100\text{ GW}$, keeping the subsurface ocean liquid. Radioactive decay in the core contributes a negligible amount of heat (less than $5\text{ GW}$).

Scientist 2
The satellite's orbit is nearly circular, meaning tidal dissipation contributes less than $2\text{ GW}$ of thermal energy. Instead, the heat is primarily generated by hydrothermal activity at the seafloor. Serpentinization reactions (water reacting with the silicate core) and radioactive decay within the core release heat at a combined rate of $95\text{ GW}$. Hot water plumes carry this energy upward into the subsurface ocean.

Scientist 3
The heat is primarily radiogenic, produced by the decay of radioactive isotopes ($^{40}\text{K}$, $^{232}\text{Th}$, and $^{238}\text{U}$) in the satellite's silicate-rich rocky core, generating a steady heat flux of $80\text{ GW}$. Tidal dissipation is negligible. Furthermore, serpentinization reactions do not occur because the core's silicate minerals have already been fully hydrated.

Based on the descriptions provided, which of the following statements represents a point of agreement among all three scientists?