For the last few years, a massive storm the size of China has been raging on Neptune. The Hubble Space Telescope first detected the storm in June 2015, with astronomers likening its clouds to the pancake-shaped ones in the children's book Cloudy With a Chance of Meatballs. Like Jupiter's famous Great Red Spot, the storm's swirling vortex created a dark blur on the planet. But while Jupiter's spot has remained for the last 200 years, Neptune's – which is full of hydrogen sulfide, a chemical compound that smells like farts – is about to die.
According to new research published in the Astronomical Journal, the spot's contrast weakened from about 7% to about 3% from 2015 to 2017, while companion clouds shifted from its offset to the center. These findings indicate the storm is in its death stages, and it's the first time the active death of a vortex has been observed as it happens.
As the below video from NASA explains, there have been several storms on Neptune in the years since Voyager 2 first chartered the planet in the 1980s. Since Voyager 2's return, astronomers have monitored storm activity on Neptune with the Hubble Space Telescope, and have observed the formation of five different storms. But because Hubble is used for so many different observational purposes, it was only able to look at Neptune every few years, always missing the "death" of these other storms. This is the first time that the technology was able to capture time-lapse images of a storm's gradual expiration.
In a statement, Michael Wong, co-author of the Astronomical Journal study and a researcher at UC Berkeley, admitted that the storm's behavior is different than what well-known studies led scientists to expect. "[Previous] dynamical simulations said that anticyclones under Neptune’s wind shear would probably drift toward the equator," said Wong. "We thought that once the vortex got too close to the equator, it would break up and perhaps create a spectacular outburst of cloud activity."
While unexpected, it's actually great news for eager scientists because, as the NASA video explains, this means there's "a lot left to learn on Neptune." For now, we're sure it's relieved to smell a little less like old farts.