Great Dark Spot

The Great Dark Spot (also known as GDS-89, for Great Dark Spot, 1989) was one of a series of dark spots on Neptune that look similar to Jupiter's Great Red Spot. In 1989, GDS-89 was the first Great Dark Spot on Neptune seen by NASA's Voyager 2 space probe. Like Jupiter's spot, the Great Dark Spots are anticyclonic storms.

But inside them, there are fewer clouds. Unlike Jupiter's spot, which has lasted for hundreds of years, these spots seem to last a shorter time, forming and disappearing every few years. From observations by Voyager 2 and the Hubble Space Telescope, we know that Neptune often has a Great Dark Spot. Not much is known about where these spots come from, how they move, or why they disappear.

Characteristics

The Great Dark Spot was found by NASA's Voyager 2 probe in the southern part of Neptune. This dark area was oval-shaped and about as big as Earth. It looked like Jupiter’s Great Red Spot, but it could move north and south over time.

Around the edges of this storm, winds blew very fast—up to 2,100 kilometers per hour! Scientists think the Great Dark Spot might be a gap in Neptune’s methane clouds. It also made large white clouds of frozen methane, high above the main cloud layer. These clouds stayed for a long time, unlike regular clouds on Earth.

Disappearance

In November 1994, scientists used the Hubble Space Telescope to take new pictures of the Great Dark Spot. They saw that it had disappeared. This made astronomers think the spot might be hiding or had gone away. Even though the Great Dark Spot was not seen, some clouds that moved with it were still there. This showed that these storms might still exist in some way. Scientists think these dark spots might fade when they get too close to Neptune's equator, or maybe for other reasons we do not know yet.

Other dark spots observed

After the Great Dark Spot was found, scientists saw more dark spots on Neptune. In 1989, the Voyager 2 space probe saw the Great Dark Spot and another spot called Dark Spot 2. This spot vanished before 1994.

Since then, the Hubble Space Telescope has kept an eye on Neptune and found more dark spots. In 1994, a dark spot appeared in the northern part of the planet and disappeared between 1998 and 2000. Another one showed up in 1996 and vanished before 1998.

In 2015, a dark spot was seen in the southern part of Neptune by the Hubble Outer Planet Atmosphere Legacy program. It moved toward the pole before disappearing in 2017. In 2016, a new spot like the Great Dark Spot appeared in the northern part and has stayed visible for several years.

In 2018, Hubble watched a new dark spot form from the start. This spot was smaller than the one found by Voyager 2 but was still bigger than the Atlantic Ocean, about 4,600 miles across. In 2020, this dark spot changed direction and started moving north instead of south. Scientists think this happened because of natural forces that keep storms stable in the northern part of the planet.

Nearby, a smaller spot called "Dark Spot Jr." was found but later vanished. Scientists are still learning how these dark spots form and why they move.

Proposed missions

Two ideas for space trips to Neptune were suggested to NASA. One idea, called Trident, was proposed in 2021 to visit Neptune and its moon Triton. But two missions to Venus, called DAVINCI+ and VERITAS, were chosen instead. Another idea, Neptune Odyssey, plans to send a spacecraft around Neptune and might launch in 2033. These missions want to learn more about Neptune’s moon Triton and its atmosphere. The China National Space Administration also looked at ways to travel to Neptune using special engine technology.