科学美国人60秒:Great Red Spot Helps Explain Jupiter's Warm Upper Atmosphere

For most people, Jupiter’s most recognizable—and mysterious—feature is the Great Red Spot. For centuries, astronomers have watched the storm spin across the giant world’s face.

But for planetary scientists, Jupiter’s most distinctive mystery may be what’s called the “energy crisis” of its upper atmosphere: how do temperatures average about as warm as Earth’s even though the enormous planet is more than fives times further away from the sun?

All the sun’s giant planets display this energy crisis, and those in chilly orbits around other stars probably have it, too. So where does the energy to heat their upper atmospheres come from?

According to a new study, the energy must originate within the giants, get transported upward and become amplified by turbulent storms. The finding appears in the journal Nature. [James O'Donoghue et al., Heating of Jupiter’s upper atmosphere above the Great Red Spot]

This offers a new window into Jupiter’s depths, and should allow researchers to better understand gas-giant atmospheres throughout the universe. And it’s all connected to the Great Red Spot.

Astronomers have long known that auroral displays can heat Jupiter’s poles, where charged particles trapped in the planet’s intense magnetic field slam into its upper atmosphere. Some theorists thought this auroral heating could flow toward the equator to warm the planet’s mid-latitudes. So, using NASA’s Infrared Telescope Facility, astronomers observed Jupiter for nine hours, looking for these flows as thermal fluctuations in the planet’s upper atmosphere.

But they saw none.

Instead, in Jupiter’s mid-latitudes they spied a thermal spike 800 kilometers above the Great Red Spot, where temperatures soared hundreds of degrees higher than the surroundings. The best way to explain this spike is from the swirling maelstrom below, where turbulent atmospheric waves must generate heat by crashing together like breakers on a windy beach shore. Though this must be a planet-wide phenomenon, it is most obvious directly over Jupiter’s largest, most powerful storm.

As alien as it seems, scientists have seen the same behavior on much smaller, gentler scales here on Earth, when thunderheads rising over mountain ranges create rippling waves that heat the air above.

—Lee Billings