Which internal heat source still generates heat within the terrestrial worlds today?

Question

Quizplus · Accepted Answer

Heat from radioactive decay is the only internal heat source that still generates heat within the terrestrial worlds today. Heat from differentiation is the heat generated when heavy materials sink to the center of a planet or moon during its formation, and this process is mostly finished within a few tens of millions of years after the planet's formation. Heat of accretion is the heat generated when small particles come together to form a larger body, but this process is also mostly finished within the first few tens of millions of years after the planet's formation. Heat from convection is a process by which heat is transferred from the interior of the planet (or moon) to its surface, but it is not an internal heat source, since it depends on the initial heat generated by differentiation or radioactive decay.

Which Internal Heat Source Still Generates Heat Within the Terrestrial