A storm the size of China on the face of Neptune is dying, and researchers who have been studying the dark vortex since it was first spotted in 2015 have no clue why.

The storm is believed to be made up of hydrogen sulfide, which smells the same as rotten eggs and farts, but everything else about it remains a mystery.

The Mysterious, Rotten-Smelling Storm Of Neptune

The mysterious storm on Neptune was first spotted by the Hubble Space Telescope in 2015. Only five of these dark vortices have been discovered on Neptune, and this most recent one, named SDS-2015, can only be detected and tracked by the same thing that found it.

The theory is that the vortices form when clouds made of air and gas in the atmosphere of Neptune swirl and then freeze due to the cold temperatures of the planet. The frozen mass drifts in Neptune's atmosphere like a giant ice pancake, and as it churns, it draws up things such as hydrogen sulfide that is believed to make it smell very bad.

The most recent photos taken by the Hubble Space Telescope of SDS-2015, however, reveal that the storm is dying. Some storms on other planets can last for a long time, such as the centuries-old Great Red Spot of Jupiter, but the storms of Neptune have relatively shorter lives.

The images taken by the Hubble Space Telescope, which can be seen in a video uploaded by the official NASA Goddard account, showed that the storm is definitely shrinking.

According to a study that was published in the Astronomical Journal, besides looking at the Hubble Space Telescope images to see how the mysterious Neptune storm dies, studying the pictures will provide more clues on how the weather system of the planet works, including what kind of winds there are on it.

Questions Remain For Neptune Storm

It is not enough to determine that SDS-2015 is a mysterious Neptune storm that smells like rotten eggs. As it fades away, there remain many questions about its existence.

First and foremost, there is no concrete explanation on how the dark vortices on Neptune start, including the factors that affect their drift and oscillation, how the storms interact with what surrounds them, and how they dissipate.

In addition, while the pending death of SDS-2015 is expected, the way that it is dying is a surprise. Researchers thought that the storm will move closer to Neptune's equator, where it will break up and generate cloud activity. However, SDS-2015 appears to be simply fading away, and it is moving to the planet's south pole and not to its equator.