Hubble just snagged a picture of a dark vortex looming over Neptune during a May 16th view of the planet. This is actually the third documented sighting of a dark vortex in Neptune’s atmosphere. It was seen in 1989, during a Voyager fly-by. Then, in 1994, Hubble spotted the strange feature again.
Dark vortices form when clouds of gas and air in Neptune’s atmosphere begin swirling and eventually freeze up in the icy temperatures, to move as a single strange mass. “Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains,” leader of the study, Mike Wong of the University of California-Berkeley said to NASA. Along with the dark vortices, comes an accompanying stream of bright clouds—which Wong notes are similar to the “clouds that appear as pancake-shaped features lingering over mountains on Earth.”
A close-up of the observed dark vortex (Image: NASA, ESA, and M.H. Wong and J. Tollefson (UC Berkeley))
All the dark vortices have a cloud of frozen gas, topped with bright clouds, but all the other features appear to be completely changeable. Differences in size, shape, and the duration they last has been noted among all the observed dark vortices.
Although this is the first time the strange feature has been spotted in 22 years, researchers suspect that other dark vortices have passed through Neptune’s atmosphere unnoticed in the meantime. In particular, an incident in 2015 raised suspicions, when astronomers worldwide reported seeing bright clouds in Neptune’s skies. Ultimately, though, they couldn’t confirm a sighting of a dark vortex beneath them.
Now that they have a better look at Hubble’s view of one of Neptune’s dark vortices, researchers hope to get a better understanding of just why they form and why they eventually disappear.