Blasting around the equators of the solar system’s giant planets — Jupiter, Saturn, Uranus and Neptune — are fierce jet streams that reach speeds of 500 to 1,500 kilometers per hour. For years, scientists have puzzled over why these extreme winds blow eastward on Jupiter and Saturn but westward on Uranus and Neptune, even though all four planets share similar conditions: each receives little sunlight, has a moderate internal heat source and rotates rapidly.
Now, researchers at the Weizmann Institute of Science have developed a new model that, for the first time, offers a single mechanism explaining this long-standing mystery. Their findings were recently published in Science Advances.
The study, led by Dr. Keren Duer-Milner as part of her Ph.D. research in Prof. Yohai Kaspi’s group in Weizmann’s Earth and Planetary Sciences Department, used hydrodynamic modeling to show that variations in atmospheric depth can account for the opposite wind directions. In other words, under the same physical conditions, a planet’s jet streams can flow either eastward or westward depending on how deep its atmosphere extends.
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Gas giants Jupiter and Saturn are encircled by eastward jet streams at the equator, whereas ice giants Uranus and Neptune are encircled by westward jet streams. The new model establishes a direct link between wind direction and atmospheric depth
“We were excited to find a simple and elegant explanation for such a complex phenomenon,” said Duer-Milner, now a postdoctoral fellow at Leiden University in the Netherlands. “Understanding these jet streams reveals fundamental processes that shape atmospheric dynamics — not only in our solar system but across our galaxy. This insight gives us a new tool for exploring the enormous climatic diversity throughout the universe.”