Neptune has a giant spinning mystery. NASA’s Hubble Telescope captured a time-lapse of the storm for the first time and found a surprising conclusion it is shrinking. A dark storm on Neptune, once big enough to cover more distance than Kashmir to Kanyakumari, is dwindling to nothing. Officially called a dark vortex, the Neptunian storm shares a few properties with Jupiter’s Great Red Spot (GRS).
Like the GRS, a dark vortex is moving in a anticyclonic direction that sweeps up material from the planet’s icy atmosphere. It is most likely that they arise from an instability in the sheared eastward and westward winds.Unlike Jupiter’s spot, which is more than 200 years old, Neptune’s dark vortex has only been visible in recent years.
It is possibly made of hydrogen sulfide, and NASA notes that it might have “the pungent smell of rotten eggs. Neptune’s is also the first dark vortex to be captured while (presumably) dying. When first spotted in 2015, the oval was 3,100 miles long. However, Hubble’s latest shots from October 2017 show it at 2,300 miles across. That many miles of rotten eggs is nothing to sneeze at, but it is shrinking nonetheless.