- The Great Red Spot is the solar system's largest storm.
- Juno revealed the storm extends 300 to 500 km deep.
- A 2024 study dates the current spot to 1831, not 1665.
Jupiter's Great Red Spot is a persistent anticyclonic storm in Jupiter's southern hemisphere, wider than Earth and sustained for at least 190 years. It is the largest known atmospheric vortex in the solar system.
Why It Matters
Key figure
16,500 km
Current width of the Great Red Spot
The Great Red Spot is the most studied storm beyond Earth. Its longevity and scale offer planetary scientists a natural laboratory for understanding atmospheric dynamics that have no terrestrial equivalent. No hurricane on Earth lasts more than a few weeks. This storm has persisted for nearly two centuries, and possibly longer.
For researchers studying how planets form and evolve, the Great Red Spot provides direct evidence of how gas giant atmospheres organize energy over long timescales. NASA's Juno spacecraft, which arrived at Jupiter in 2016, has transformed our understanding of the storm's three-dimensional structure and its relationship to the planet's deep interior.
The spot also serves as a benchmark for comparative planetology. Astronomers studying storm systems on Saturn, Neptune, and even exoplanet atmospheres use Jupiter's Great Red Spot as a reference point for modeling vortex behavior in hydrogen-helium atmospheres.
How It Works
The Great Red Spot sits at roughly 22 degrees south of Jupiter's equator, wedged between two powerful jet streams flowing in opposite directions. The northern jet moves westward; the southern jet moves eastward. The storm's rotation is counterclockwise (anticyclonic in the southern hemisphere), driven by the shear between these opposing flows.
Key figure
432 km/h
Peak wind speed at the storm's edge
Unlike Earth's hurricanes, which are low-pressure systems fed by warm ocean water, the Great Red Spot is a high-pressure system embedded in a gaseous atmosphere with no solid surface beneath it. Wind speeds at the storm's outer ring reach 432 km/h (268 mph). Hubble Space Telescope observations between 2009 and 2020 showed that these outer winds accelerated by roughly 8 percent over that period, according to a 2021 analysis by Michael Wong at the University of California, Berkeley.
Juno's microwave radiometer scans during a July 2017 flyby revealed that the storm extends 300 to 500 kilometers below Jupiter's visible cloud tops. That depth surprised researchers. The storm's roots reach 50 to 100 times deeper than Earth's oceans, and the base is warmer than the top, suggesting the vortex taps into thermal energy from Jupiter's interior.
The storm's reddish color remains incompletely understood. The leading hypothesis involves ultraviolet sunlight breaking down ammonia and acetylene in the upper atmosphere, producing reddish compounds called chromophores. Since 2014, the color has deepened to an intense orange, though the mechanism behind this shift is not yet resolved.
Key Context
In June 2024, Agustin Sanchez-Lavega of the University of the Basque Country published a study in Geophysical Research Letters arguing that the current Great Red Spot is not the "Permanent Spot" that Giovanni Cassini first recorded in 1665. By comparing historical size and position data, Sanchez-Lavega's team concluded that Cassini's spot likely disappeared between the mid-18th and 19th centuries. The current storm was first reliably documented in 1831. Numerical simulations suggest it formed from an instability between Jupiter's opposing zonal jets, not from merging smaller vortices.
The storm is also shrinking. In the late 1800s, the Great Red Spot measured roughly 40,000 km across its long axis. Voyager 1 recorded 23,300 km in 1979. By 2024, Hubble measured approximately 16,500 km, with the shape shifting from oval to nearly circular. The shrinkage rate accelerated starting around 2012, losing roughly 930 km per year. Whether the storm will eventually dissipate or reach a stable smaller size is an open question in planetary science.
FAQ
Is Jupiter's Great Red Spot a hurricane?
No. It is an anticyclone, meaning it is a high-pressure system that rotates opposite to hurricanes. Earth's hurricanes are low-pressure systems fueled by warm oceans. The Great Red Spot has no ocean beneath it and rotates counterclockwise in Jupiter's southern hemisphere, the opposite direction of southern-hemisphere cyclones on Earth.
How old is Jupiter's Great Red Spot?
The current storm dates to at least 1831, based on a 2024 study by Sanchez-Lavega and colleagues. An earlier Permanent Spot observed by Giovanni Cassini beginning in 1665 is now considered a different, separate storm that disappeared before the 19th century.
Will the Great Red Spot disappear?
It is shrinking. The storm has lost more than half its length since the late 1800s, and the rate of shrinkage accelerated after 2012. Some models suggest it could become circular by 2040, but whether it will vanish entirely or stabilize at a smaller size is unknown.
Why is the Great Red Spot red?
The exact cause is uncertain. The leading explanation involves ultraviolet radiation breaking down ammonia and acetylene high in Jupiter's atmosphere, producing reddish compounds called chromophores. The color has deepened since 2014. Laboratory experiments at NASA's Jet Propulsion Laboratory have partially replicated the color, but no single chemical pathway fully accounts for the observed hue.
Related Reading
Sources
- Primary Research: The Origin of Jupiter's Great Red Spot (Sanchez-Lavega et al., Geophysical Research Letters, 2024)
- Additional Context:
- NASA's Juno Probes the Depths of Jupiter's Great Red Spot (NASA, 2021)
- Hubble Shows Winds in Jupiter's Great Red Spot Are Speeding Up (NASA, 2021)
- The depth of Jupiter's Great Red Spot constrained by Juno gravity overflights (Parisi et al., Science, 2021)
- Great Red Spot (Encyclopaedia Britannica)
Fact Check: Claim-by-Claim Verification Verified
All major claims verified against NASA, peer-reviewed papers, and Encyclopaedia Britannica. No inaccuracies found.
Sources used for verification
- The Origin of Jupiter's Great Red Spot - agupubs.onlinelibrary.wiley.com
- NASA's Juno Probes the Depths - science.nasa.gov
- Hubble Wind Speed Analysis - science.nasa.gov
- Juno Gravity Overflights - science.org
- Great Red Spot - britannica.com
