The Hubble Space Telescope unveiled a new and mysterious dark storm on Neptune and provided a fresh look at a long-lasting storm that surrounds the North Polar region on Uranus, NASA said.
Like Earth, Uranus and Neptune have seasons, which probably drives some of the features in their atmospheres, according to the US space agency.
However, their seasons are much longer than on our planet, spanning decades instead of months, NASA said in a statement.
The storm appeared during the southern summer of the planet, the fourth and last mysterious dark vortex captured by Hubble since 1993.
Two other dark storms were discovered by the Voyager 2 spacecraft in 1989 while flying on the remote planet, NASA said.
Since then, only Hubble has had the sensitivity in blue light to track these hard-to-detect features, which appeared and quickly vanished.
A study conducted by Andrew Hsu, a university student at the University of California, Berkeley in the United States, estimated that dark spots appear every four or six years at different latitudes and disappear after about two years.
Hubble discovered the last storm in September of last year in the northern hemisphere of Neptune. The characteristic is approximately 6,800 miles wide.
To the right of the dark feature there are bright white companion clouds. Hubble has observed similar clouds that accompany previous vortices.
Like the Great Red Spot of Jupiter, the dark vortices swirl in an anticyclonic direction and seem to extract material from deeper levels in the ice giant’s atmosphere.
The Hubble observations show that as early as 2016, the increase in cloud activity in the region preceded the emergence of the vortex.
The images indicate that the vortices probably develop deeper into Neptune’s atmosphere and become visible only when the top of the storm reaches higher altitudes.
The snapshot of Uranus, like the image of Neptune, reveals a dominant characteristic: a vast cloud layer of storm around the north pole.
Scientists believe that this new feature is the result of the unique rotation of Uranus. Unlike all other planets in the solar system, Uranus is tilted almost sideways.