Scientists have solved the mystery of Saturn's rotation for the first time in decades

Scientists have for the first time traced in detail how auroras on Saturn affect the planet's atmosphere and create the illusion of changes in its rotation speed. Research using the James Webb Space Telescope helped solve a mystery that had puzzled astronomers for decades. The work was published in the Journal of Geophysical Research: Space Physics (JGRSP).

The problem arose after observations by the Cassini spacecraft in 2004. The data obtained indicated that Saturn's rotation speed changes over time. This seemed strange, since planets cannot noticeably speed up or slow down over such short periods of time.

In 2021, a team of researchers led by Tom Stallard from Northumbria University proposed an explanation. It turned out that it was not the planet's rotation itself that was changing, but the electrical signals associated with auroras. These are influenced by winds in the upper layers of the atmosphere, causing rotation speed calculations to be distorted. However, the origin of these winds remained unknown.

To understand the mechanism behind the phenomenon, the scientists used the James Webb Telescope. It continuously observed Saturn's northern aurora over the course of a full Saturnian day. The researchers analyzed infrared emissions from the H₃⁺ ion — a molecule that serves as a temperature indicator in the gas giant's upper atmosphere.

The new observations were approximately ten times more precise than previous measurements. They made it possible to compile the most detailed maps of temperatures and charged particle distribution in the auroral region. Thanks to this, scientists discovered localized zones of atmospheric heating and cooling for the first time.

The analysis showed that energy arriving during auroras heats specific areas of the atmosphere. The resulting temperature contrast drives winds that generate electric currents. These currents, in turn, sustain the auroras themselves, forming a closed cycle.

"Essentially, we are observing a planetary heat pump. The auroras heat the atmosphere, the atmosphere creates winds, the winds generate currents that fuel the auroras. The system sustains itself," Stallard explained.

According to the authors of the study, the discovery has significance beyond Saturn alone. It demonstrates that a planet's atmosphere and magnetosphere can be closely linked and constantly exchanging energy. The researchers suggest that similar processes may occur on other planets in the Solar System and beyond.