When NASA’s Voyager 2 visited Neptune, in 1989, scientists noticed immense dark storms swirling in its atmosphere.
Since then only the Hubble Space Telescope has had the ability to spot and track these mysterious storms.
Hubble found a pair of these dark storms in the mid-1990s and then noticed they later had disappeared completely.
The latest storm to be observed first appeared in 2015, but scientists have noticed that it too is shrinking out of existence.
It’s the first time Hubble has photographed one of these storms as it continues to die.
Some liken Neptune’s storms to Jupiter’s Great Red Spot.
But while the giant planet’s huge swirling storm system has been observed for hundreds of years, scientists found Neptune’s storms last only for a couple of years.
It’s thought the storms may be made of hydrogen sulfide, which on Earth smells like rotten eggs.
This series of Hubble Space Telescope images taken over 2 years tracks the demise of a giant dark vortex on the planet Neptune. (NASA, ESA, and M.H. Wong and A.I. Hsu (UC Berkeley))