VLA Finds Megastorms on Saturn Disrupt Gas Giant’s Deep Atmosphere in Surprising Ways

A study of rare megastorms on Saturn using data from the National Science Foundation’s Karl G. Jansky Very Large Array has revealed disruptions in the distribution of ammonia gas in the planet’s deep atmosphere. The findings raise questions about just how different gas giants can be from each other, and challenge scientists’ understanding of how megastorms may form on planets other than Earth. The results of the study appear in Science Advances.

When seen in the optical, Saturn’s banded atmosphere appears to smoothly shift from color to color. But seen here in radio light, the distinct nature of these bands is apparent. Scientists used VLA data to better understand ammonia in the gas giant’s atmosphere and learned that megastorms transport the ammonia from the upper to the lower atmosphere. Credit: S. Dagnello (NRAO/AUI/NSF), I. de Pater et al (Berkeley)

2. It takes radio eyes to see what these storms are doing to Saturn

Megastorms occur approximately every 20-30 years and are similar to hurricanes on Earth, although significantly larger. But there is one major difference: on Earth hurricanes draw their energy from the underlying warm ocean. On Saturn hurricanes form without oceanic assistance. That led the team to wonder how weather patterns form on the gas giant, what energy is sustaining them, and what other unique mechanisms or outcomes result from them. To find out more about these giant storms, the team had to probe layers in the atmosphere below the clouds, which are invisible to the human eye. That’s why the team turned to the VLA.

Imke de Pater, an astronomer at UC-Berkeley, and a co-author on the study, has been studying gas giants with the VLA for over four decades to better understand their composition and what makes them unique. “At radio wavelengths, we probe below the visible cloud layers on giant planets. Since chemical reactions and dynamics will alter the composition of a planet’s atmosphere, observations below these cloud layers are required to constrain the planet’s true atmospheric composition, a key parameter for planet formation models,” she said. “Radio observations help characterize dynamical, physical, and chemical processes including heat transport, cloud formation, and convection in the atmospheres of giant planets on both global and local scales.”

3. Megastorms have put ammonia on the move