The Winds of Jupiter’s Great Red Spot Are Speeding Up

Jupiter has distinguished by the presence of its huge storm known as the Great Red Spot for ages, maybe almost as far back as the first telescope. However, the location has changed over time, shrinking and growing, and potentially disappearing entirely. Its most recent alteration, as seen through the Hubble telescope, is that the winds in the Spot’s outer regions are slowly accelerating. We do not know why, like with so many other features of this massive vortex. Every six Earth days, the Spot rotates counterclockwise (14 days on Jupiter). Given its enormous size, the Spot’s outskirts, known as the high-speed ring, require wind speeds of hundreds of kilometers per hour.

Since 2009, the Hubble Space Telescope has been monitoring the red spot with a sensor that can detect wind speeds at different places. The winds along the Spot’s edge have increased by 8% between 2009 and 2020, according to an analysis published in Geophysical Research Letters. No one noticed earlier since the increase was too moderate and constant for those who only checked in on a regular basis. The speed of the outermost winds has increased by less than 2.7 kilometers per hour per year (1.6 miles per hour). However, over time, this has added up to an extra 25 km/h (15.5 mph) – a respectable wind all by itself. Surprisingly, the already reduced speeds in the center have slowed even more.

“‘Does this make sense?’ I wondered when I first saw the data. No one has ever seen something like this before “Dr. Michael Wong of the University of California, Berkeley, was the study’s first author, according to a release. “However, Hubble is the only one who can do this. This discovery is made feasible by Hubble’s longevity and continuing observations.”

Other Jovian meteorological events have occurred during the time the Great Red Spot has been with us, including a convective storm that passed near to the Spot in 2017, generating a rapid increase in windspeeds. Hubble can only observe the Spot’s cloud tops, which rise 8 kilometers (5 miles) above the surrounding cloud tops before descending at the edges. As a result, Wong says he has no idea what’s going on beneath the surface that’s causing it to accelerate. The report eliminates a few possibilities, but Wong and his co-authors are not sure what the answer is.

The Great Red Spot on Jupiter is the largest and longest-lasting weather phenomenon in our Solar System. It began shrinking at the turn of the century after being deemed largely steady for more than a century, losing half its width by 2004 and more since then. Even in its current state, the Spot is huge enough to fit the Earth inside, and it could once have fit three piles of earth side by side. The shrinking cannot explain by variations in wind shear, according to the report.

The first confirmed sightings of the location were in 1830. From 1665 through 1713, a similar red stain was observed in Jupiter’s southern hemisphere. This was most likely the same storm that we see now, but it shrank for a century beyond the reach of telescopes of the time, only to rebound. Unfortunately, we do not know how strong the winds were at the time.