Atmospheric water may be giving Saturn its spots

Every 20 to 30 years, Saturn gets hit with a giant thunderstorm. Such storms, dubbed “Great White Spots,” cover the planet and have been observed since 1876. Moisture in the planet’s atmosphere may be suppressing normal storm formation for decades at a time, so when conditions allow, the storms that form are enormous, researchers suggest April 13 in Nature Geoscience.

Planetary scientists Cheng Li and Andrew Ingersoll at Caltech modeled how water might drive the storm cycle on Saturn. By their calculations, heavy water molecules prevent warm air, which is full of lighter hydrogen and helium, from rising and triggering storms. Over time, cooling in the upper atmosphere eventually drives warm, wet air up, and a giant storm erupts across the planet.