Jupiter’s Great Red Spot in 2018, as seen by the Juno spacecraft. Credit: Enhanced Image by Gerald Eichstadt and Sean Doran (CC BY-NC-SA) based on images provided Courtesy of NASA/JPL-Caltech/SwRI/MSSS. Image courtesy AGU.

Jupiter’s Great Red Spot is Not the Spot We Thought

Oops! New analysis reveals Cassini’s 1665 superstorm discovery was not the one we see today

Robert Roy Britt
Aha! Science
Published in
3 min readJun 19, 2024

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Giovanni Domenico Cassini was a great sketcher of the sky. The Italian-born French astronomer would peer through one of the crude telescopes of his time, and draw what he saw. Now, thanks in part to his illustrations, a longstanding assumption in astronomy has been overturned.

Cassini’s drawings of the Permanent Spot on Jupiter in the 1600s (a-c). For comparison, (d) shows the current Great Red Spot, taken by Eric Sussenbach. Credit: AGU

Astronomers have long thought Cassini discovered Jupiter’s Great Red Spot, that whirling vortex of Jovian winds so huge it’s visible through backyard telescopes. That would make the hurricane-like storm 359 years old. But new research indicates the spot Cassini spotted faded away, and the one we see today is a wholly different storm whipped into existence about two centuries ago.

Permanent spot? Not!

The fresh debunking, published this week in the journal Geophysical Research Letters, was possible thanks not just to Cassini’s sketches, but also subsequent illustrations by other observers.

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Robert Roy Britt
Aha! Science

Editor of Aha! and Wise & Well on Medium + the Writer's Guide at writersguide.substack.com. Author of Make Sleep Your Superpower: amazon.com/dp/B0BJBYFQCB