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Interesting submission to Geophysical Research Letters on ArXiv today: https://arxiv.org/abs/2406.13222
The authors discuss the origin and evolution of the GRS, including that the current GRS wasn’t the same object observed by Cassini.This has certainly long been John Roger’s view, that Cassini’s spot was not the current one. 19th Century drawings and early photographs show the GRS as a huge pale area at that time, unlike Cassini’s more concentrated dark spot. It seems likely Cassini was seeing a late stage of a contracting, darkening and accelerating spot, just as we are now seeing the similar late phase of the 19th C GRS.
Yes, their historical account is essentially the same as in my 1995 book, which fortunately they do cite thoroughly — and brought up to date, of course. The idea that the GRS formed from a South Tropical Disturbance was also proposed in my book. What’s new, and very welcome, is that they have done computational simulations that show this to be physically plausible.
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