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Will Saturn’s shenanigans ever end? Scientists have discovered that the ringed planet has massive seasonal energy imbalances across its surface.
The discovery marks a turning point in our understanding of the gas giant’s weather and climate, its long-term evolution, and ongoing changes.
“This is the first time that a global energy imbalance on a seasonal scale has been observed on a gas giant,” said physicist Li-Min Li of the University of Houston. “This not only provides new insights into planetary formation and evolution, but also changes how we think about planetary and atmospheric science.”
What this means is that the Sun’s intense light, which spreads throughout the solar system, gives energy to everything it hits. Energy is also lost by the planets in the form of cooling, and is radiated back into space, mainly in the form of thermal radiation.
In the case of gas giant planets, including Saturn, energy sources are active deep within the planet, influencing the planet’s climate from within.
When a team led by atmospheric scientist Xinyue Wang of the University of Houston was combing through Cassini data to study Saturn’s brightness, they noticed something intriguing: The amount of energy Saturn absorbs and releases varies by up to 16 percent, and this variation coincides with Saturn’s seasons.
When the researchers dug deeper, they found that it has to do with how far Saturn is from the Sun at any given time: Saturn’s orbit isn’t a perfect circle, but is actually an ellipse (a property called eccentricity), which results in a difference in distance of about 20 percent between its closest and furthest distances to the Sun.
When Saturn is closer to the Sun, it receives much more radiation from the Sun than when it is farther away, creating a seasonal energy imbalance. This is completely different to how Earth works: Saturn’s orbit is more circular, so Earth doesn’t experience the same sharp contrast.
In fact, no one expected gas giants either.
“Current models and theories about the atmosphere, climate, and evolution of gas giants assume that the global energy budget is in balance,” Wang explains, “but our discovery of seasonal energy imbalances calls for a reevaluation of these models and theories.”
This could mean that Saturn’s unbalanced energy may play a previously unrecognized role in generating giant convective storms that reach deep into the atmosphere, and that similar processes may be at work on other gas giants, such as Jupiter, which has a slightly lower eccentricity than Saturn.
It may also help us understand a bit more about Earth’s weather, where the energy imbalance is much smaller, but still not zero. And the interior and exterior workings of those other gas-shrouded planets, Neptune and Uranus, are largely unexplored and remain mysterious to us humans.
“Our data suggest that these planets also have significant energy imbalances, and we predict that Uranus will have the strongest imbalance due to its orbit’s eccentricity and very high inclination. [tilt]” says Wang.
“Our current investigations are aimed at identifying the limitations of current observations and developing testable hypotheses that can inform future flagship missions.”
Never change, Saturn.
This study Nature Communications.
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