BALTIMORE, June 23 (UPI) -- There's a new dark spot on Neptune, the farthest planet from the sun.
Astronomers recently confirmed the presence of a dark vortex spinning across the planet's atmosphere after examining imagery collected by the Hubble Space Telescope last month. It's the first Neptune vortex discovered since 1994.
The high pressure system is accompanied by bright companion clouds. Researchers believe the clouds are formed as the vortex pushes ambient air higher into the atmosphere, forcing gases to freeze into methane ice crystals.
"Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains," Mike Wong, a researcher astronomer at the University of California, Berkeley, said in a news release. "And the companion clouds are similar to so-called orographic clouds that appear as pancake-shaped features lingering over mountains on Earth."
Wong led the investigation of Hubble data that yielded the discovery of the new dark spot.
Jupiter hosts similar cyclone-like disturbances, but the gas giant's vortices are more uniform and sometimes persist, slowly evolving, for decades. Previous studies have proven Neptune's vortices to be a permanent feature, but the disturbances are shorter-lived.
The last several Neptune vortices seen by astronomers have exhibited a wide range of sizes and shapes, and have proven to be relatively unstable -- wandering north and south, speeding up and slowing down.
Scientists hope further monitoring of Neptune's vortices will illuminate how they originate and the factors that influence their fluctuations.