You and I may think of the Great Red Spot as Jupiter’s defining characteristic, but Jupiter himself is rather embarrassed about his spot. He’s been trying for some time now to get rid of it.
The Great Red Spot (or G.R.S., as all the cool kids call it) has been shrinking for decades now, and the rate of shrinkage has been accelerating. Just this year, long streams of red stuff seemed to break free, as it the G.R.S. were “unspooling.”
So why has the G.R.S. gone into decline? Well, a better question might be why did it last so long in the first place? Apparently, according to most fluid dynamics models, the G.R.S. should have only lasted a few years. Instead, it’s been going strong for centuries. Astronomers first noticed it as early as 1664.
In 2013, physicists Philip Marcus of U.C. Berkley and Pedram Hassanzadeh of Harvard gave us a partial answer. According to this article from phys.org, they were the first to model the G.R.S. not as a 2D surface feature but as a 3D structure, with a vortex extending into the depths of Jupiter’s atmosphere.
Marcus and Hassanzadeh found that vertical flow (hot and cold air moving up and down inside the G.R.S.) was doing a lot to help keep the storm system going. As Hassanzadeh explains in that same phys.org article:
In the past, researchers either ignored the vertical flow because they thought it was not important, or they used simpler equations because it was too difficult to model.
Late last month, Marcus and Hassanzadeh gave a presentation at the annual meeting of the American Physical Society, and according to that presentation, fans of the Great Red Spot have nothing to worry about.
As Marcus explains in this article for Astronomy Magazine, we can monitor the vortex beneath the G.R.S. by observing the behavior of other nearby storm systems. And based on those observations, Marcus says, “[…] there is no evidence that that vortex itself has changed its size or intensity.”
Personally, I think Marcus and Hassanzadeh make a pretty compelling case that the G.R.S. is as strong as ever, even if it appears, superficially, to be shrinking. But I still don’t really understand what’s caused that superficial shrinkage, and I’m left wondering how long it will be before the visible part of the G.R.S. starts to expand again. Surely it will start expanding again, right?
I guess there’s always more to learn.
Planet Pailly 
So the biggest thunderstorm you’ve ever seen building on the horizon is just a hint of what the GRS must be?
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That sounds right to me. The thing about storms on Earth, though, is that there’s always a solid (or liquid) surface beneath them. Storms on Jupiter can extend much farther down, and that changes how they work and how long they can last.
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I can only imagine what the model must look like. Millions of calculation cells? Yikes
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I’m sure it’s more math than I would ever want to think about.
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Jupiter with the Great Red Spot just wouldn’t be Jupiter. Hope it survives.
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I think there’s a pretty compelling case that it will survive. But of course only time will tell.
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Seems like an iceberg essentially, bobbing up and down in the ocean of Jupiter’s gases.
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That analogy might not be far off.
Also, if I remember correctly, at one point people hypothesized that the G.R.S. might literally be an iceberg floating in an ocean of liquid hydrogen. This was way before the Voyager missions, of course.
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I wonder if the red spot would be like Neptune’s great dark spots in that once the current spot disappears another one might come up
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Probably. I seem to remember at some point a couple smaller red spots appeared and disappeared in Jupiter’s atmosphere. So there could be an ongoing process that makes these things.
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