Something very strange has happened to Neptune. In the last few years, the pale cloud streaks that usually adorn the blue atmosphere have almost completely disappeared. Also, images from 1994, when the Hubble Space Telescope began documenting Neptune for the first time, show that this is not the first time. The fluctuations also seem to be related to another periodic variation, the 11-year activity of the solar cycle.

Given that Neptune is about 4.5 billion kilometers away, or just over 30 times the average distance between Earth and the Sun, the discovery surprised and intrigued astronomers.

And the final transformation was particularly dramatic. Clouds in mid-latitudes began to disappear in 2019. By 2020, the planet looked more or less cloudless.

“Even four years later, the images we took last June showed that the clouds had not returned to their former levels,” says astronomer Erandi Chavez of Harvard University, who was at UC Berkeley at the time of conducting the research.