Saturn’s Energy is Out of Balance

Earth releases about as much energy out into space as it absorbs, arriving at a thermal equilibrium. This means it will reach an average temperature as is the case with most planets. Saturn however, is a little different as recent observations show the planet’s energy is out of balance. It seems that in addition to the energy it receives from the Sun, there must also be an internal source of heat, perhaps driven by its highly elliptical orbit. 

Saturn is the sixth planet from the Sun and is most well known for its stunning ring system. It was the first celestial object I saw through a telescope and like many others, captured my imagination. Of all the planets Jupiter is the largest followed by Saturn which has an equatorial diameter (not including the rings) of 116,460 kilometres. 

The Cassini spacecraft began its journey to Saturn in 1997. After a seven year journey it arrived in 2004 and until 2017 studied the ringed planet. It carried an array of scientific instruments including high resolution cameras to capture stunning detail of the planet and its rings. It also explored some of Saturn’s moons and made many discoveries such as the confirmation of the subsurface ocean on Enceladus and the hydrocarbon lakes on Titan. 

It was using the data form Cassini that Xinyue Wang, a third year doctoral student from the Natural Sciences and Mathematics department of University of Houston made their fascinating discovery. They found an imbalance in the planets atmospheric energy levels that seemed to vary on a seasonal cycle. Just like Earth, every other planet gets energy from the Sun. This solar radiation is absorbed and then re-emitted as thermal radiation. Wang reported ‘Saturn, like the other gas giants, has another energy input in the form of deep internal heat affecting its thermal structure and climate.’

The team conclude that the imbalance which recurs on a seasonable basis must have ben due to it’s large orbital eccentricity by nearly 20%. This refers to the elliptical orbit of Saturn which takes it closer to the Sun and then further away on a regular basis. As it gets closer to the Sun it experiences a massive increase in incoming solar radiation and less as it slowly drifts further away. Conversely, Earth which has a much smaller orbital eccentricity does not experience changes in the magnitude of incoming solar radiation.

Understanding the increased incoming radiation (which takes place for a number of years)  before slowly dropping again) is key to understanding the dynamics of the planet’s atmosphere. The development of giant storms is one effect as these are more prominent when there is an increase in incoming radiation. Studying these changes may help us to develop a better understanding of Earth’s atmospheric processes too. 

Until now we believed that there was no energy imbalance. This recent study revealed that this is not the case and it now requires further study to assess and develop the models. Along with further studies of the Saturnian energy imbalance, the team now wish to study the other gas giant planets and expect they will find similar imbalances. 

Source :  UH Scientists Discover Massive Energy Imbalance on Saturn