Hubble Space Telescope Sees Shrinking Dark Spot on Neptune

Neptune’s dark storms were first discovered in the 1980s by NASA’s Voyager 2 spacecraft.

Since then, only Hubble has had the sharpness in blue light to track these elusive features that have played a game of peek-a-boo over the years.

Hubble found two dark storms that appeared in the mid-1990s and then vanished.

This latest storm was first seen in 2015, but is now shrinking.

Like Jupiter’s Great Red Spot (GRS), the storm swirls in an anti-cyclonic direction and is dredging up material from deep inside the ice giant planet’s atmosphere.

The elusive feature gives astronomers a unique opportunity to study Neptune’s deep winds, which can’t be directly measured. The dark spot material may be hydrogen sulfide.

“The particles themselves are still highly reflective; they are just slightly darker than the particles in the surrounding atmosphere,” said Dr. Joshua Tollefson, from the University of California, Berkeley.

Unlike Jupiter’s GRS, which has been visible for at least 200 years, Neptune’s dark vortices only last a few years. This is the first one that actually has been photographed as it is dying.
“We have no evidence of how these vortices are formed or how fast they rotate,” said Dr. Agustín Sánchez-Lavega, from the University of the Basque Country.
“It is most likely that they arise from an instability in the sheared eastward and westward winds.”
The dark vortex is behaving differently from what planet-watchers predicted.
“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect,” said Dr. Michael Wong, from the University of California, Berkeley.

 Source :- sci-news