Jupiter’s Great Red Spot: Perpetual Storm Shrinks, But Isn’t Dying

The space photo of the week is this beautiful panorama of Jupiter’s Great Red Spot. It is one of the most photographed storms in our solar system.

The Great Red Spot has been a well-known landmark of the largest gas planet in our solar system for hundreds of years. In 1665, Italian astronomer Gian Domenico Cassini spotted a so-called “permanent spot” on Jupiter. In the centuries that followed, various drawings, sketches and beautiful photographs of space telescopes and craft of this perpetual storm followed. The well-known vortex on Jupiter appeals to the imagination. However, astronomers see the storm getting smaller and smaller. And that is worrying.

At the end of the nineteenth century, the Great Red Spot had a diameter of about 50,000 kilometers. In 1979, the Voyager spacecraft observed the Jovian storm and its length was estimated at 23,000 kilometers. The storm was therefore about half smaller than more than a hundred years earlier. Over the past decade, the storm has shrunk again, and astronomers have seen the area around the spot transform. For example, spacecraft Juno saw the red cloud cover differ. Also, tufts of red clouds came loose from the Great Red Spot. Would it mean the storm is dying?

Fortunately, this doesn’t seem to be the case. The cloud cover is slowly shrinking, but the vortex itself is very much alive. “While cloud cover probably affects the vortex, it’s not critical to its maintenance,” said study researcher Philip Marcus of the University of California, Berkeley. “To understand the health of the Great Red Spot, we must examine the health of the vortex and not that of the cloud cover; the shrinking of the cloud alone is not an indication that the storm is dying. Judging by the interaction between the Great Red Spot and other vortices and the surrounding jet streams, there is no evidence whatsoever that the vortex itself has become smaller or less powerful.”

This mosaic consists of two photos. The photos were stitched together by citizen scientist Kevin M. Gill. The two photos were taken on February 12, 2019 by the Juno spacecraft. Juno flew 70,000 above the cloud tops of Jupiter at the time.

The Great Red Spot is not only very large, but also very deep. Scientists used Juno’s microwave radiometer to peek beneath Jupiter’s turbulent cloud tops. The Great Red Spot appears to be up to 350 to 500 kilometers deep. “This means that the Great Red Spot is 50 to 100 times deeper than Earth’s oceans,” said Caltech professor Andy Ingersoll. Suppose you were to swim to the bottom of the Great Red Spot, then the temperature would increase. “This heat difference causes violent wind storms, which we see at the top of the atmosphere.”

Scientists think the Great Red Spot is also warming Jupiter’s atmosphere. Previously, the upper part of Earth’s atmosphere has been found to be about as warm as the upper part of Jupiter’s atmosphere. That’s strange, because our atmosphere and Jupiter’s are heated by the sun, but Jupiter is five times farther from the sun than our planet. It suggests that the sun is not the only source of heat for Jupiter’s atmosphere. Recent research provides more clarity. Researchers recorded the temperature high above Jupiter’s clouds using a telescope on Earth. By studying the invisible infrared light hundreds of kilometers above the gas giant, the researchers found that temperatures in the vicinity of the Great Red Spot were much higher.

“The extremely high temperatures we observed above the storm are evidence of this energy transfer,” said study researcher James O’Donoghue. “This tells us that planet-wide warming is a plausible explanation for the temperatures in the higher parts of the atmosphere being hundreds of degrees higher than can be explained by sunlight alone.”

Our planet fits into the Great Red Spot exactly once.