The existence of the high-pressure system known as a dark vortex was confirmed by Hubble Space Telescope of NASA.
"Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains," research astronomer Mike Wong, of the University of California at Berkeley, said in a statement. Wong led the team that analyzed the Hubble data.
"And the companion clouds are similar to so-called organic clouds that appear as pancake-shaped features lingering over mountains on Earth," he added.
The quest to see the bright clouds on the ice giant was started by both professional and amateur astronomers in July 2015. Companion clouds form when air flowing on the planet is disturbed and cast upward by a dark vortex.
After reaching a certain height, the gas freezes into methane crystals, forming clouds. This provided the first hint of a newly formed vortex, since the high-pressure systems are typically only visible at blue wavelengths.
Hubble's Outer Planet Atmospheres Legacy (OPAL) project was launched to create global maps of the outer residents of the solar system each year. It was turned towards Neptune by the researchers in September 2015.