Published on Feb 13, 2019
Hubble Space Telescope has uncovered a new mysterious dark storm on Neptune and provided a fresh look at a long-lived storm circling around the north polar region on Uranus. Like Earth, Uranus and Neptune have seasons, which likely drive some of the features in their atmospheres. But their seasons are much longer than on Earth, spanning decades rather than months. The new Hubble view of Neptune shows the dark storm, seen at top center. Appearing during the planet's southern summer, the feature is the fourth and latest mysterious dark vortex captured by Hubble since 1993. Two other dark storms were discovered by the Voyager 2 spacecraft in 1989 as it flew by the remote planet. Since then, only Hubble has had the sensitivity in blue light to track these elusive features, which have appeared and faded quickly. A study led by University of California, Berkeley, undergraduate student Andrew Hsu estimated that the dark spots appear every four to six years at different latitudes and disappear after about two years. Hubble uncovered the latest storm in September 2018 in Neptune's northern hemisphere. The feature is roughly 6,800 miles across. The snapshot of Uranus, like the image of Neptune, reveals a dominant feature: a vast bright stormy cloud cap across the north pole. Scientists believe this new feature is a result of Uranus' unique rotation. Unlike every other planet in the solar system, Uranus is tipped over almost onto its side. Because of this extreme tilt, during the planet's summer the Sun shines almost directly onto the north pole and never sets. Uranus is now approaching the middle of its summer season, and the polar-cap region is becoming more prominent. This polar hood may have formed by seasonal changes in atmospheric flow. Near the edge of the polar storm is a large, compact methane-ice cloud, which is sometimes bright enough to be photographed by amateur astronomers. A narrow cloud band encircles the planet north of the equator. 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. Read more at: https://phys.org/news/2019-02-hubble-... https://www.iflscience.com/space/hubb...