Three billion miles away on the farthest known major planet in our solar system, an ominous, dark storm – once big enough to stretch across the Atlantic Ocean from Boston to Portugal – is shrinking out of existence as seen in pictures of Neptune taken by NASA’s Hubble Space Telescope.
Immense dark storms on Neptune were first discovered in the late 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.