Energy Imbalance On Titan

Abstract:

Radiant energies of planets and moons are of wide interest in the fields of geoscience, astronomy, and planetary sciences. Titan’s global radiant energy budget is assumed to be balanced in all current theories and studies. Here we show that the emitted thermal energy is not balanced by the absorbed solar energy on Titan with the long-term multi-instrument observations from the Cassini spacecraft. During the Cassini era (2004-2017), the global energy imbalance is 2.73±0.46% of the emitted thermal energy. For a complete Titan year (29.4 Earth years), the imbalance is even larger (4.78±0.91% of the emitted energy). The energy imbalance suggests that current theories and models of Titan’s atmosphere should be re-examined. Earth’s small energy imbalance (~0.2-0.4% of the emitted energy) plays critical roles in global warming, so Titan’s energy imbalance has important impacts on its climate system. Possible energy imbalance should be examined for other terrestrial bodies. Finally, the seasonal variations of Titan’s radiant energies suggest that the time-varying energies must be considered in the estimate of the internal heat of giant planets.