Space, US study: on Neptune the clouds have disappeared for the first time

On Neptune, the clouds have almost completely disappeared, an extraordinary and unexpected event that was discovered by researchers at the University of California at Berkeley and published in the scientific journal Icarus. It is the first time that this phenomenon has occurred in almost 30 years of observations. In fact, the planet’s atmosphere appears devoid of cloud formations, with the exception of the South Pole area. Despite the considerable distance from the Sun, their disappearance seems to be connected to the activity of our star.

The first close-up observation of Neptune in 1989

Neptune is the outermost planet and one of the coldest in our Solar System and has so far only been explored by the Voyager 2 probe in 1989, when it made a close flyby passing just 5,000 kilometers away from the icy giant. During this mission, a large storm had been discovered taking place on the gaseous planet’s surface. Over the years, scientists have observed Neptune using powerful instruments such as the Keck telescope in Hawaii and the Hubble and Webb space telescopes.

According to the study, the disappearance of clouds depends on the Sun

The images collected over time have made it possible to study the evolution of clouds in Neptune’s atmosphere. The white clouds, similar to terrestrial cirrus, have reduced considerably in recent months. Analyzing the collected data, the scientists found a possible correlation between clouds and the solar cycle, a period of about 11 years characterized by fluctuations in the intensity of solar radiation. According to the study authors, the peaks in ultraviolet light emission from the Sun coincided with an increase in cloud formations on Neptune, with a delay of about 2 years. This discovery could shed new light on the understanding of atmospheric mechanisms and phenomena related to solar activity on outer planets such as Neptune.

Study lead researcher: “Extraordinary data”

“These extraordinary data give us the strongest evidence that Neptune’s cloud cover is related to the Sun’s cycle,” said Imke de Pater, lead researcher on the study. “Our findings – he added – support the theory that the sun’s UV rays, when strong enough, could trigger a photochemical reaction that produces Neptune’s clouds.” A correlation that amazed the researchers since Neptune receives only a little more than a thousandth of solar radiation compared to the Earth but demonstrates the great observational capabilities available today: “Being able to use telescopes on Earth to study the climate of a world more than four billion kilometers from us is fascinating,” said Carlos Alvarez, an astronomer at the Keck Observatory and one of the authors of the study.