Jupiter’s Great Red Spot – a storm larger than our entire planet – is one of the most visible features in the Solar System, believed to date back to shortly after the invention of the telescope, if not much earlier. However, new evidence suggests that it instead formed in 1831 and was mistaken for a continuation of a previous blob from the previous century, making it much, much younger than previously thought.
Galileo’s adaptation of the telescope for astronomical purposes revealed features such as Jupiter’s moons and sunspots for the first time. As instruments improved, astronomers noticed that Jupiter had dark and bright bands parallel to its equator, with dark spots sometimes appearing at normally white latitudes.
In 1665 Giovanni Cassini, immortalized for discovering the largest gap in Saturn’s rings, was probably the first to report the dark oval later known as the “Permanent Spot”. However, the 1832 report may have been about the same thing. Because the spot rotated with Jupiter, it could only be seen for about five hours at a time before disappearing on the far side, but if the viewer was patient, it always returned while other spots came and went. That is, until 1713, when she disappeared into invisibility and disappeared for 100 years.
By 1831, the spot was back, attracting the name The Great Red Spot, or so the conventional story goes. Books about the wonders of the Solar System generally state that the storm shrunk to be too small for modest telescopes in the 18th century.Thursday century to pick up before it rebounds. Given that the Great Red Spot has changed many times over nearly two centuries—currently frustrating amateur astronomers by shrinking to about the size of Earth—this story seems highly plausible.
However, according to new research, this is also wrong. Instead, the team led by Professor AgustÃn Sánchez-Lavega of the Universidad del PaÃs Vasco says the Permanent Spot and the Great Red Spot are probably unrelated, making the current spot just 193 years old.
He painted Jupiter in 1881, depicting the enormous size of the spot at the time. Jupiter is upside down due to the telescope used.
Image credit: Thomas Gwyn Elgar Public Domain
The Permanent Spot and the Great Red Spot are located in Jupiter’s lower to mid-southern latitudes, leading astronomers to associate them. However, the Great Red Spot is, well, red, although we still don’t know why (it also has a blue spot, although it’s not actually blue). We have records of astronomers reporting seeing the Fixed Spot many times over the years; the authors of the new study note that neither applies to color, although the 1711 painting shows a red hue.
Telescopes improved only slowly during the 118 years that Jupiter was relatively unblemished, but astronomical giants like Charles Messier and William Herschel described the planet with telescopes better than their predecessors without reporting anything at this latitude.
The researchers also say that the patch we currently see is likely the result of disruptions in the flow of the zonal jets to the north and south of it. This contrasts with more common explanations: the merging of several smaller eddies or a superstorm. The team modeled the formation of an anticyclonic superstorm on Jupiter based on Saturn’s giant 100-year storms. However, regardless of their assumptions, they always got something smaller than the early descriptions of the Great Red Spot. Anticyclonic eddies coalesce on Jupiter, but the authors found that to form something as large as the Great Red Spot, it would have to spin much faster than it currently does.
Adjusting the age of the spot would fundamentally change the way we see Jupiter’s atmosphere. If a spot has been there since at least 1665, then it is likely that it was there long before that, perhaps millions of years, and no one had the capacity to observe it. A storm rising 8 kilometers (5 miles) above the rest of Jupiter’s clouds would then be considered an almost permanent part of our Solar System, and its current contraction is expected to change soon.
On the other hand, if this analysis is correct, the Great Red Spot may be on its last legs, trying to reach the 200-year mark before disappearing in a cloud of ammonia-enriched hydrogen.
The modern Spot is sometimes compared to a giant spinning eye, but it seems that if Jupiter is tracking the smaller planets, it comes with long blinks.
An awful lot happened between 1665 and 1831, so if the Great Red Spot had actually formed by the time the news restarted, it would be younger than intercity railroads (1830) and computers (1822). However, he is slightly older than Jonathan, the world’s oldest living turtle.
The study is open access in Geophysical Research Letters.