Even though planetary astronomers have already noticed Neptune`s dark spot in the past, this phenomenon still raises many questions. The first vortex was observed in 1989 when the Voyager 2 flew by Neptune. This space probe was launched in 1977, and ever since it helped researchers gather valuable information about planets such as Uranus, Neptune, Jupiter, and Saturn.
At this moment, it has already left the solar system, and it`s one of the most distant human-made objects in the entire Universe.
The second time scientists observed Neptune`s dark spot was in 1994. With the help of Hubble Space Telescope, an optical device launched into Earth`s orbit in 1990, experts noted the existence of this phenomenon once more.
However, this is the first time the dark vortex is observed in the 21st century. The images were taken by NASA`s HST (Hubble Space Telescope) on the 16th of May, 2016. The following day, the discovery was revealed to the public.
The Neptune`s dark spot, also known as the Great Dark Spot, was compared on many occasions with Jupiter`s Great Red Spot. Both phenomena are similar in the sense that they represent anticyclonic storms. However, unlike the red spot noticed on the surface of Jupiter, which has lasted for hundreds and hundreds of years, this one appears to have a shorter lifespan.
Scientists assume that the lifetime of such a spot is limited to only a few years. Following several measurements, experts estimate that the winds around this vortex blow up with a speed of 2,400 kilometers an hour. According to the data gathered so far, these are the fastest winds in the solar system.
Another particularity of the dark vortex is represented by the bright companion clouds formed around the spot. Mike Wong, the researcher who led the team that investigated the phenomenon, compared Neptune`s white clouds with the orographic clouds on Earth, which we can observe above the picks of mountains, and distinguish them due to their conical shape.
However, while the clouds on Earth are made of ice crystals, Neptune`s are made of frozen methane.
Scientists hope to study this phenomenon further in order to understand exactly how it`s formed, what are the atmospheric conditions that favor its appearance and also how it eventually dissipates.
Image source: Wikipedia