It’s difficult to imagine the magnitude of storms on Jupiter. The gas giant’s most visible atmospheric feature, the Great Red Spot, may be getting smaller, but one hundred years ago, it was about 40,000 km (25,000 miles) in diameter, or three times Earth’s diameter.
Jupiter’s atmosphere also features thunderheads that are five times taller than Earth’s: a whopping 64 km (40 miles) from bottom to top. Its atmosphere is not entirely understood, though NASA’s Juno spacecraft is advancing our understanding. The planet may contain strange things like a layer of liquid metallic hydrogen.
Now a group of scientists are combining the power of the Hubble Space Telescope, the Gemini Observatory and the Juno spacecraft to probe Jupiter’s atmosphere, and the awe-inspiring storms that spawn there.
Michael Wong, from UC Berkeley, is leading the team behind this work. The team includes Imke de Pater, who’s also at UC Berkeley, and Amy Simon. Simon is from NASA’s Goddard Space Flight Center (GSFC.)
The team is combining close up views of Jupiter provided by Juno, with multi-wavelength observations from the Hubble and the Gemini Observatory. The results of their work is published in a paper titled “High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019.” It’s published in The Astrophysical Journal: Supplement Series.
In a press release, Wong said summed up the project, saying “We want to know how Jupiter’s atmosphere works.”
Jupiter’s atmosphere is in a constant state of turmoil, and the scale of the storms dwarfs those on Earth. Those storms involve massive lightning bolts, up to three times more energetic than ours. Luckily, those bolts are like radio transmitters, and Juno can hear them. Every 53 days the spacecraft performs a fly-by of Jupiter.
At those times, it can “hear” the bolts, and their radio signals known as “sferics” (short for “radio atmospheric signals”) and “whistlers.” Scientists use those signals to map out the lightning bolts, even if they’re obscured from view, deep in Jupiter’s enormous atmosphere.
Hubble and Gemini are taking part in this new combined observing program. Each time Juno comes close to Jupiter and hears the signals from the lighting bolts, Hubble and Gemini capture global images of the planet. Those images are key to interpreting and understanding Juno’s data.
“Juno’s microwave radiometer probes deep into the planet’s atmosphere by detecting high-frequency radio waves that can penetrate through the thick cloud layers,” Simon explained in a press release. “The data from Hubble and Gemini can tell us how thick the clouds are and how deep we are seeing into the clouds.”
The team’s method makes use of Hubble visible light images and Gemini thermal infrared images. The images are combined, and the Juno lightning flashes are mapped onto the images. As a result, the team of scientists have shown how lightning storms are “associated with a three-way combination of cloud structures: deep clouds made of water, large convective towers caused by upwelling of moist air — essentially Jovian thunderheads — and clear regions presumably caused by downwelling of drier air outside the convective towers.”
The Hubble data show the height of the thick clouds in the convective towers, as well as the depth of deep water clouds. The Gemini data clearly reveal the clearings in the high-level clouds where it is possible to get a glimpse down to the deep water clouds.
In the press release, Wong explained some of the team’s findings. Wong says that there is a type of area in Jupiter’s atmosphere called a folded filamentary region. That’s where moist convection is taking place, and where lightning is common. “These cyclonic vortices could be internal energy smokestacks, helping release internal energy through convection,” he said. “It doesn’t happen everywhere, but something about these cyclones seems to facilitate convection.”
Jupiter is the Solar System’s largest planet, and discovering more about it tells us more about the rest of the Solar System. By correlating lightning with deep water clouds, researchers are better able to estimate how much water is in Jupiter’s atmosphere. That’s important because it gives clues to how Jupiter formed. Not only Jupiter, but other gas giants as well, even the Solar System itself.
And even though scientists have studied Jupiter intensely, there’s a whole lot they don’t know. At the top of the list might be the question of how much water it has in its deep atmosphere. We also don’t have a solid understanding of how heat flows from the interior, and what’s causing the colors and shapes of the clouds. This new effort is giving some understanding of how Jupiter’s atmosphere is structured, and how it behaves.
Jupiter’s most-observed feature has to be the Great Red Spot (GRS), a baffling shape that humans have been watching since at least 1830.
Thanks to all the attention that Jupiter’s getting from the Hubble and from Gemini, scientists are studying short-term changes in the GRS. There are dark features inside the GRS that astronomers have seen in images as they come and go. But this observing program is giving astronomers a unique opportunity to watch those features more closely.
As it turns out, those dark features that appear in visible light are the opposite in infrared: they’re bright patches instead. That means they’re actually holes in the clouds. Heat from Jupiter’s deeper layers is escaping through the holes in the clouds, easily seen in infrared images from Gemini.
“It’s kind of like a jack-o-lantern,” said Wong. “You see bright infrared light coming from cloud-free areas, but where there are clouds, it’s really dark in the infrared.”
The study outlines how other features in Jupiter’s atmosphere function, especially how different chemicals cycle through the atmosphere, changes in wind direction, and the nature of different sized cyclones. The authors emphasize how effective the combined observing power of the Hubble, Gemini, and Juno at unlocking some of Jupiter’s secrets.
“Because we now routinely have these high-resolution views from a couple of different observatories and wavelengths, we are learning so much more about Jupiter’s weather,” explained Simon. “This is our equivalent of a weather satellite. We can finally start looking at weather cycles.”
There’s a lot more science to be done with the data that Wong and the team have collected. There’s no way to anticipate all of the discoveries it could lead to. Data from the Cassini mission is still leading to new discoveries about Saturn and its moons, and the same may be true for Juno once its mission is ended. The team behind this study is making all of their data accessible so that others can access it in their own work.
“What’s important is that we’ve managed to collect this huge data set that supports the Juno mission. There are so many applications of the data set that we may not even anticipate. So, we’re going to enable other people to do science without that barrier of having to figure out on their own how to process the data,” Wong said.