Field notes on things that run themselves
A Storm With No Walls
Point a backyard telescope at Jupiter on a steady night and, once your eye relaxes into the blur, you may catch it: a pale salmon oval riding one of the planet’s southern stripes, small in the eyepiece and unreasonably large in fact. It is a single storm, and you could lower the whole Earth into it with room to spare. It has been turning, by the most careful count, since before anyone now alive was born — since before the telescope in your hands was anything like modern. The Great Red Spot is the most famous weather on any world but ours, and almost nothing about it is solid.
Last issue ended on a wave that lived for minutes: a phantom traffic jam, a knot of stopped cars sliding backward through a freeway, gone the instant the traffic thinned. The same trick, it turns out, can run for centuries. Issue No. 2 was a standing wave you could wade into — a shape held in place by water rushing through it. Shrink that idea and speed it up and you get a jam; blow it up to the width of a planet and slow it to a stately roll, and you get the Spot. A pattern with nothing at its center, held up by flow — only here the flow is an entire atmosphere, and the standing has lasted lifetimes.
What is actually out there is an anticyclone: a high-pressure storm spinning the “wrong” way, counterclockwise in Jupiter’s southern sky, its rim winds running near 430 kilometers an hour. A parcel of cloud caught at the edge takes about six days to make one full lap of the oval. And it does not wind down, because there is nothing for it to wind down against. Jupiter is a gas planet — no ground to rub on, no coastline to break against, no floor to bleed its spin into. Better still, the Spot is wedged between two of Jupiter’s jet streams running in opposite directions, east above and west below, like a ball bearing trapped between two conveyor belts turning opposite ways: caught, spun, and held in its lane. It is even fed. Smaller storms drift into it and are swallowed, each one topping up its rotation. When Juno’s gravity measurements sounded its depth, the roots reached only a few hundred kilometers down — deep for a storm, but thin against its sixteen-thousand-kilometer breadth. A vast, shallow coin of wind, spinning between two rivers of air.
So how old is it? Here the honest answer is stranger than the legend. In 1665 Giovanni Cassini reported a dark mark in about the right latitude — a “Permanent Spot,” seen on and off until 1713. Then the record goes dark. For more than a century, from 1713 to 1830, no one wrote down a spot at all. The storm we photograph today was first drawn in 1831 and has been watched without a real break since the 1870s. In 2024 a team led by Agustín Sánchez-Lavega modeled those old sightings and concluded that Cassini’s Permanent Spot most likely faded away, and that today’s Great Red Spot is a different storm that flared up around 1831. If they are right, the longest-lived storm we know is younger than the U.S. Constitution — and the deeper marvel is not its age but the gap. The same patch of Jupiter grew a giant red storm, lost it, and grew another. The place outlived the storm.
And the present one is going the way of the first. A century of measurements shows it narrowing: roughly three Earths across in the late 1800s, about two at the Voyager flybys of 1979, and near one and a tenth today — the smallest it has ever been measured. As it narrows it stretches taller, like clay rolled thin and pushed up. Hubble recently caught it wobbling in size and brightness on a ninety-day cycle, as though something were gently squeezing it. The leading suspect for the long shrink is starvation: fewer of the small storms it used to eat are arriving, and a vortex that lives by swallowing loses ground when the meals stop coming.
Run all ten issues together and the Spot is the thesis carried to its edge. A flame keeps its shape while its substance burns away; a language keeps its shape while its speakers die; a heartbeat keeps its shape while the very molecules that beat are swapped out underneath it. The Great Red Spot keeps its shape while not just its air but, apparently, its own past blows through and leaves. Every cloud that ever wound through it shredded long ago. Perhaps the entire storm did once, and the planet simply grew another in the same place, out of the same banded winds and the same trapped heat. What persists, in the end, may not be the storm at all but the conditions that summon one — the standing wave behind the standing wave. We have always called it permanent, and we are half right. The shape is. The thing never was.
One loop I’m watching
The Spot keeps its shape by spinning; the next one keeps its shape by dying and rebuilding. A coral reef looks like rock — old, hard, finished — but it is closer to a city than a stone: a living crust whose architects, the coral polyps, are forever dying and being replaced, each thin generation cementing its skeleton onto the bones of the last. The limestone stays; almost nothing alive in it does. And the whole edifice is propped up by a quiet bargain with an alga living inside the coral’s own cells. Next time: a wall of life built entirely by its own dead.
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