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Researchers at the University of Houston have discovered a significant energy imbalance on Saturn, providing new insights into planetary science and challenging existing climate models for gas giants. The findings are published in Nature Communications.
“This is the first time that a global energy imbalance on a seasonal scale has been observed on a gas giant,” said Liming Li, physics professor in the UH College of Natural Sciences and Mathematics. “Not only does this give us new insight into the formation and evolution of planets, but it also changes the way we should think about planetary and atmospheric science.”
Using data from the Cassini probe mission, Xinyue Wang, a third-year doctoral student in NSM’s Department of Earth and Atmospheric Sciences, identified a significant and previously unknown seasonal energy imbalance on Saturn.
“Every planet gets energy from the sun in the form of solar radiation and loses energy by emitting thermal radiation,” Wang explained. “But Saturn, like other gas giants, has another energy input in the form of deep internal heat affecting its thermal structure and climate.”
The imbalance arises due to Saturn’s large orbital eccentricity, which varies by nearly 20% from aphelion (the point farthest from the sun) to perihelion (the point closest to the sun), resulting in substantial seasonal variations in absorbed solar energy. In contrast, Earth does not experience a significant seasonal energy imbalance due to its small orbital eccentricity.
“Earth does have a measurable energy budget, but it’s primarily determined by absorbed solar energy and emitted thermal energy,” said atmospheric sciences professor Xun Jiang. “Earth’s internal heat is negligible, and its seasons last only a few months compared to several years on Saturn.”
The data suggests that Saturn’s unbalanced energy budget plays a key role in developing giant storms, which dominate its atmospheric system. This information may also provide insights into Earth's weather patterns.
“To our knowledge, the role of energy budget in developing moist convective storms on Earth has not been fully examined,” Wang noted. “We plan to investigate that as well to see if there’s a connection.”
The Cassini mission was an ambitious collaboration between NASA, the European Space Agency, and the Italian Space Agency. It launched in 1997 and explored Saturn for nearly 20 years. Professor Li was selected as a participating scientist to monitor three onboard instruments observing Saturn’s radiant energy budget.
Wang conducted this study with fellow graduate students Larry Guan (physics), Thishan D. Karandana G., Ronald Albright (earth and atmospheric sciences), under advisement from professors Li and Jiang.
“In current models of gas giants’ atmosphere, climate, and evolution, it is assumed that their global energy budgets are balanced,” Wang stated. “But our discovery necessitates reevaluating those models.”
Li's team plans further research on other gas giants like Uranus where they predict similar imbalances due to its high orbital eccentricity and obliquity.
“Our data suggests these planets will have significant imbalances as well,” Wang said. “What we’re investigating now will identify limitations in current observations and formulate testable hypotheses benefiting future missions.”
In addition to UH researchers, authors include scientists from NASA; universities such as Wisconsin-Madison; Maryland; Central Florida; California Santa Cruz; France's Université Côte d’Azur; Spain's University of Basque Country among others.