Images taken with the Hubble Space Telescope by UC Berkeley planetary scientist Michael Wong, who led the Outer Planet Atmospheres Legacy program, or OPAL, confirmed the existence of a dark vortex in Neptune’s atmosphere.
The presence of the dark vortex was verified in May and was the first sighting of a dark vortex on Neptune in the 21st century. Dark vortices are high-pressured systems made of swirling masses of gas and air that eventually condense into a single mass, moving through the atmosphere like huge, gaseous mountains.
“(Dark vortices) help us understand the altitude of Neptune, because when they drift it gives us an idea of what the background atmosphere is (that) they’re drifting through,” Wong said. “The vortices give us a test of what the weather is.”
Amy Simon, part of the OPAL team and the senior scientist for Planetary Atmospheres Research at NASA, said dark vortices are typically accompanied by a stream of bright companion clouds. She likened the accompanying bright clouds to the ones that form over the tops of ordinary mountains.
The OPAL team suspected the dark vortex’s existence when they sighted it last September, a suspicion that was confirmed after the team was awarded time to use the Hubble Space Telescope in May. Joshua Tollefson, a UC Berkeley earth and planetary science graduate student collaborating on the study, said only the Hubble Space Telescope has a high enough resolution to see vortices on the distant planet, which, he added, was why the telescope was essential to confirm the team’s previous evidence.
The team was intrigued by the appearances and reappearances of the dark vortices on Neptune compared to the vortices on Jupiter, which have remained stagnant for centuries. Tollefson said one possible explanation for this discrepancy between vortices on the two planets is that Jupiter’s belts — which differ in altitude — restrict the movement of the vortices, while the vortices on Neptune can move toward the equator and eventually dissipate.
“If you compare the vortex on Neptune to the one on Jupiter that’s lasted for centuries, there’s clearly key differences driving them,” Tollefson said. “We don’t understand them yet.”
Wong said it is going to be an exciting time to study Jupiter as Hubble and many ground based observatories will be devoting resources to taking observations using Juno, an unmanned spacecraft headed to Jupiter that will enter its orbit starting July 4. Wong added that the dissipation of the Neptune vortex is predicted to be accompanied by erupting clouds in its vicinity, which is why the team hopes to continue tracking and observing it.
“The dissipation is something that we really want to observe because it’s predicted to be pretty spectacular,” Wong said. “It’s never been observed before.”