Yearly monitoring of these giant worlds is now allowing scientists to study long-term seasonal changes, as well as capture transitory weather patterns.
During a routine sweep of the outer solar system, the Hubble Space Telescope caught a new and mysterious "dark vortex" in the clouds of Neptune, according to NASA. Uranus, which is in its summer season, also has a more prominent polar-cap region that might be a result of atmospheric flow changes.
This image, taken by Hubble's Wide Field Camera 3 (WFC3), shows a new dark storm (top center) on Neptune.
In contrast to Earth, where seasons last only a couple of months, Neptune and Uranus experience seasons that keep going for quite a long time, bringing about weird and intense atmospheric phenomena. The new data, captured during the autumn of 2018, are providing important new insights into the seasonal variations on both Neptune and Uranus. However, due to our planet's atmosphere, a storm like the large dark vortex on Neptune is unlikely to happen here.
Storms like this appear every four to six years in different parts of the planet and disappear after about two years, NASA reported.
Since then Hubble has sufficient sensitivity in the blue light, and is able to track these elusive features that appear and disappear quickly.
This latest vortex was photographed by Hubble in September 2018 during a scan of Neptune's northern hemisphere. These clouds form when air is redirected over the vortex, which causes the gases in the air to freeze as methane ice.
NASA and the Space Telescope Science Institute (STScI) announced the discovery of the storm on Thursday. Since the Hubble started tracking the storms, increased cloud activity has been a regular precursor to their appearance. The scientists hypothesized that these large vortices born deep in the Neptune's atmosphere, where gases like helium and hydrogen are more prevalent than in the upper atmosphere. It's now mid-summer at Uranus' north pole, resulting in the protracted white cap.
The white cap is most likely the result of the planet's unique rotation - unlike every other planet in the system, Uranus has made a decision to rotate counterclockwise. "Unlike every other planet in the solar system", NASA explained. Because of this extreme tilt, during the planet's summer the Sun shines nearly directly onto the north pole and never sets. Whereas Earth's worst storms typically last no more than days or weeks, Neptune's newest dark vortex is expected to last years.
At the edge of the storm is a compact methane-ice cloud. But as time progressed, a reflective band-whitish against Uranus' blue hues-began to appear encircling the north pole. "It is a mystery how bands like these are confined to such narrow widths, because Uranus and Neptune have very broad westward-blowing wind jets".