Jupiter is weirdly hot.
For a planet so far from the sun, its upper atmosphere is a boiling 400 degrees Celsius (750 Fahrenheit). That's about the same as Earth's upper atmosphere.
"Jupiter is five times farther from the sun than Earth, so it receives less than 4% the amount of heating by sunlight than Earth, so they shouldn't be similar at all," James O'Donoghue, a planetary scientist at the Japan Aerospace Exploration Agency (JAXA), told Insider via email.
In fact, he added, Jupiter should be about -100 degrees Celsius based on sunlight alone. Scientists have long wondered what makes the planet's outer layers so hot. This mystery is known as Jupiter's "energy crisis."
O'Donoghue found a clue when he spotted a heat wave traveling south from Jupiter's north pole in 2017. It began with electrically charged particles from the sun, which bombarded the north pole, caused an aurora there, and heated the region to 700 degrees Fahrenheit. Then Jupiter's winds carried that heat south.
O'Donoghue mapped that aurora and the resulting heat wave in the animation below. He's still studying the features of the heat wave, which he presented at the Europlanet Science Congress in September.
The discovery indicates that Jupiter's auroras may keep the planet's upper atmosphere so astonishingly hot.
"We essentially solved it," O'Donoghue said.
Jupiter's aurora drove a heat wave as wide as 10 Earths
Just like on Earth, Jupiter's auroras come from a steady stream of charged particles flowing out from the sun. When an eruption occurs on the sun, it sends an extra flood of those particles, which travel along Earth's magnetic field lines to the poles and interact with particles in our atmosphere to create the beautiful dancing lights of the aurora.
The same thing happens on Jupiter — though the planet also gets electrically charged particles from volcanic eruptions on its moon, Io.
O'Donoghue published his team's first research linking Jupiter's aurora to planet-wide heating in 2021. They learned that global winds push heat from the poles toward the equator. They think auroras are constantly heating the planet's upper atmosphere, but big surges of aurora activity also drive big heat waves like the one they spotted in 2017.
"After the auroras caused the atmosphere to heat up, the heat would cause the atmosphere to expand and spill both toward the equator and toward the polar cap, which is exactly what we see with this giant wave," O'Donoghue said.
In their new research this year, O'Donoghue's team mapped the heat wave in more detail. They learned it rushed toward the equator at a speed of thousands of kilometers per hour. The heat wave extended 130,000 kilometers across Jupiter. That's as wide as 10 Earths.
They think the aurora storm and resulting heat wave came from a surge of plasma from the sun.
O'Donoghue said scientists need to record more heat waves on Jupiter to confirm that auroras are behind them.
In 2020, another team of researchers found auroras were behind Saturn's "energy crisis" as well. These colorful ribbons of electromagnetic particles from the sun are proving to be significant players in other planets' atmospheres.
