The upper atmosphere above Jupiter’s Great Red Spot — the huge storm that has been raging for centuries on the gas giant — is much hotter than anywhere else on the planet. New research published today in Nature suggests that movement of the massive storm in Jupiter’s lower atmosphere may be responsible for the extra high temperatures in the upper layer. And that means that the two atmospheres may be connected and influence each other.
The Great Red Spot is one of the most iconic features of Jupiter. It’s a giant hurricane that spans more than 1,000 miles across the planet, and contains winds that move up to 400 miles per hour, according to NASA. The Great Red Spot has been continuously observed since the late 1800s, with astronomers trying to understand how the storm started and what the atmosphere is like around it.
The lower atmosphere and the upper atmosphere of Jupiter are connected
Now, using measurements from the NASA Infrared Telescope Facility in Hawaii, the researchers found that the region is about 1,600 Kelvin, or more than 2,400 degrees Fahrenheit — much toastier than the average temperature found throughout the rest of Jupiter’s upper atmosphere, which is around 900 K, or 1,1160 degrees Fahrenheit. The shift in temperature may be due to high-energy waves, the study authors say. That means that the turbulent movements of the massive storm create acoustic waves that shoot upward. These energetic waves then shake the atoms in the upper atmosphere, creating the large spike in temperatures.
The finding suggests that the lower atmosphere and the upper atmosphere of Jupiter are actually connected in a way — that one region affects the others. That’s surprising given the upper atmosphere of Jupiter is about 500 miles higher than the lower atmosphere. "We didn’t think those two regions could be coupled in any significant way, but it turns out they are," said lead researcher James O’Donoghue, a planetary scientists at Boston University.
This coupling may also help to explain a mystery
This coupling may also help to explain a mystery that’s plagued planetary scientists for years, known as the "Energy Crisis." It has to do with the fact that the upper atmospheres of Jupiter — and all the other gas giants in our Solar System — are much hotter than they should be. Computer models show that Jupiter’s upper atmosphere should be around 300 degrees Kelvin, or about 80 degrees Fahrenheit, based on how far away it is from the Sun, according to O’Donoghue. But direct observations show that its upper atmosphere is much hotter than that. Researchers weren’t really sure how to explain this heat discrepancy before, but today’s study suggests that maybe the heating is coming from the motions of the atmosphere below.
Originally, it was thought that the aurorae at Jupiter’s poles may be spreading downward and heating up the rest of the atmosphere. But models have shown that’s probably not likely, according to O’Donoghue. The aurorae mostly stay trapped at the poles, thanks to super fast winds traveling east to west in the middle of Jupiter. The other explanation was the acoustic wave idea, but there was never any direct evidence of that happening. Now after observing temperatures over the Great Red Spot, the researchers have provided an example of that process at work.
An illustration of how the Great Red Spot sends waves into the upper atmosphere. (Art by Karen Teramura, UH IfA, James O’Donoghue)
"A good analogy for this is it’s pretty much like stirring a cup of coffee with a spoon," said O’Donoghue. "If you’re stirring it clockwise, but then you suddenly stir it anti-clockwise, there will be a lot of sloshing around... And that sloshing around, you can actually hear that. It indicates there are actually some sound waves coming from that sloshing." That’s basically what’s happening at the Great Red Spot. As the storm spins anti-clockwise, it slams against the flow of the lower atmosphere and creates a lot of turbulence. That sends acoustic waves up vertically, which then vibrate the atoms in the upper atmosphere.
Similar processes happen on Earth, too
Similar processes happen on Earth, too. When air moves over the Andes mountains, for example, the collision of the air into the rock sends up acoustic waves into the upper atmosphere and causes slight heating. Even above hurricanes and tsunamis on Earth, the upper atmosphere becomes slightly warmer.
Now that the researchers have a pretty good idea of what’s happening over the Great Red Spot, they think this might also be happening elsewhere on Jupiter. They plan to look at smaller storms on the planet and eventually create a comprehensive temperature map of its upper atmosphere. Additionally, NASA’s Juno spacecraft recently inserted itself into orbit around Jupiter, and it will get some of the closest measurements of the planet to date. The vehicle may be able to confirm similar types of heating above smaller storms. It will also be studying the Great Red Spot, though Juno is more concerned with looking below the storm. "This paper argues that the Great Red Spot is responsible for a significant heating of the atmosphere above it," said Juno researcher Mike Janssen, a senior research scientist at NASA’s Jet Propulsion Laboratory. "What Juno will do is help explain what is responsible for the Great Red Spot itself."