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.