Jupiter’s ‘Great Red Spot’ Is Shrinking — And Scientists Think They Know Why
Look at any image of Jupiter and one feature is hard to ignore—its “Great Red Spot,” a massive storm raging close to its equator.
It’s so iconic that it’s unusual to see an image of Jupiter without it, despite the fact that Jupiter rotates once in just under 10 hours.
That spot, however, is shrinking. Scientists now think they know why.
Swirling Oval
A storm roughly the diameter of Earth, the Great Red Spot, is in Jupiter’s southern hemisphere and has been raging since at least 1831. A swirling, red-orange oval of high pressure more than 10,000 miles wide, it has 425 miles per hour winds that blow counterclockwise.
That makes it not a cyclone, but an anticyclone.
There are many unknowns about this massive storm. Astronomers don’t know how old it is, why it formed or why it’s red. What they do know is that it’s been getting smaller over the last 100 years, particularly in the last 50 years.
Smaller Storms
Now, new research is figuring out why the Great Red Spot is shrinking. Revealed in a paper published in the journal Icarus, a series of 3D simulations of the Great Red Spot and Jupiter’s atmosphere included interactions between it and smaller storms. The results suggest that the presence of other storms strengthens the Great Red Spot, causing it to grow larger. Without them, it shrinks.
“We found through numerical simulations that by feeding the Great Red Spot a diet of smaller storms, as has been known to occur on Jupiter, we could modulate its size,” said Caleb Keaveney, lead author and a Ph.D. student in Yale’s Graduate School of Arts and Sciences.
Earth’s Weather
The work has implications for predicting extreme weather on Earth. High-pressure systems in the westerly jet streams that circulate across Earth’s mid-latitudes—a major factor in heat waves and droughts—may be linked to high-pressure eddies and anticyclones.
“Our study has compelling implications for weather events on Earth,” said Keaveney. “Interactions with nearby weather systems have been shown to sustain and amplify heat domes, which motivated our hypothesis that similar interactions on Jupiter could sustain the Great Red Spot. In validating that hypothesis, we provide additional support to this understanding of heat domes on Earth.”
Potato-Shaped Moon
In May, Juno returned an image of the moon Amalthea above Jupiter’s “Great Red Spot.” According to NASA, a tiny potato-shaped moon with a radius of just 52 miles (84 kilometers), Amalthea is the reddest object in the solar system. That could be because it gives out more heat than it receives from the sun, possibly because electric currents are induced in the moon’s core.
However, since Amalthea takes less than half a day to orbit Jupiter, its temperature could be due to tidal stresses caused by Jupiter’s gravity, which creates a lot of friction and heat within it.
Planetary scientists had not seen an image of the moon since 2000 when NASA’s Galileo spacecraft revealed impact craters, hills and valleys on Amalthea.
