Thermal and structural evolution of Uranus

Understanding Uranus’ low luminosity is a longstanding challenge in planetary science. Simple adiabatic evolution and structure models are inconsistent
with the measured low luminosity of Uranus. This implies that the planet is non-adiabatic due to the existence of thermal boundary layers and/or conductive regions. Gradual composition distribution, if stable, acts
as a thermal boundary to suppress convection and slow
the internal cooling.
We present new models of the thermal and structure
evolution of Uranus. We assume different primordial
composition distributions, and identify the models that
fit Uranus measured properties (mass, radius, luminosity, and J2) at present time. We find several alternative non-adiabatic internal structures that fit the available measurements. It is found that Uranus’ current
structure cannot be very different from its primordial
structure, since convective-mixing in the ice giants is
limited, unlike in the case of the gas giants. Our models are consistent with a metal-rich outer envelope of
Uranus and the predictions for its magnetic field location.