An unexpected cooling effect in Saturn’s upper atmosphere

摘要: The four Solar System giants are too hot. That is, their upper-atmosphere temperatures higher than predicted by absorption of sunlight. favoured explanation is that the 'missing' heat injected magnetosphere in planets' polar regions, and redistributed globally winds. A new study rules this out. Smith et al. report net effect winds driven energy inputs on Saturn not to but cool atmosphere. This surprising result will stimulate a search for an unknown source energy, or some other process heats low latitudes directly. numerical model shows heat, low-latitude thermosphere. allows us rule out known as solution crisis at Saturn. upper atmospheres giant planets exhibit high temperatures1,2 cannot be explained sunlight2,3. In case models solar heating2,4 ∼200 K, compared ∼400 K observed independently regions5 30° latitude6. unexplained ‘energy crisis’ represents major gap our understanding these planets’ atmospheres. An important candidate missing magnetosphere1,2,4,7,8,9, which injects mostly regions planet. input believed sufficient explain temperatures9, provided it efficiently winds4,8, well understood. Here we show, using model4, There either unknown—and large—source or, more probably,