New analysis of data collected by the U.S. space agency’s Cassini spacecraft may have solved what has been a mystery to scientists for years: What keeps the upper layers of Saturn so warm?
The warmth of Saturn and other gas giants in the solar system has puzzled scientists because the planets are too far from the sun for it to be the source of the heat that has been found in their atmospheres.
But the authors of a report published this week in the scientific journal Nature Astronomy used NASA's Cassini probe data to make the most detailed examination yet of Saturn’s temperatures and atmospheric density.
They discovered auroras – similar to Earth’s northern lights – active at the planet's north and south poles. The researchers believe the auroras, electrical currents triggered by interactions between solar winds and charged particles in the atmosphere, are what’s providing the heat.
This complete picture of how heat circulates in Saturn’s atmosphere allows scientists to better understand how these auroral electric currents drive winds and distribute energy around the planet, and why the upper atmosphere is twice as hot as temperatures expected from the sun’s heat alone.
The Cassini space probe, managed by NASA, was an orbiter that observed Saturn for more than 13 years. In September 2017 it exhausted its fuel supply and was plunged into the planet, in part to protect Saturn’s moon, Enceladus, which Cassini discovered might hold conditions suitable for life.