Does Jupiter emit its own energy or does it just re-radiate sunlight?
Jupiter, Saturn, and Neptune radiate about twice as much energy to space as they receive from the sun. This is in contrast to the terrestrial planets Mercury, Venus, Earth, and Mars, which all radiate to space almost exactly the amount of energy received from the sun. In other words, the terrestrial planets are in energy equilibrium with the solar energy input, but the outer planets, at least Jupiter, Saturn, and Neptune, are not. It is theorized that the excess energy being radiated from the outer planets results from heat trapped in the interior of the planet during the time when the planet was accreting material and condensing early in the formation history of the solar system. Some gravitational contraction is continuing even at present and contributes to the energy being released. How this interior energy flow, as well as sunlight, gets distributed in the atmosphere is an important question, which relates to how and where the clouds are formed and what drives the winds. The Galile
