Uranian Hurricane (context image)

Caption NASA originale:"Just as we near the end of the hurricane season in the Atlantic Ocean, winds whirl and clouds churn 2 BMs away in the atmosphere of Uranus, forming a dark vortex large enough to engulf two-thirds of the United States.
Lawrence Sromovsky of the University of Wisconsin-Madison leads a team that used NASA's HST to take the first definitive images of a dark spot on Uranus. The elongated feature measures 1.100 by 1.900 miles (such as about 1.700 by 3.000 Km).
There have been prior unconfirmed sightings of dark spots on Uranus, including sketches made in the early 1900s, low-contrast ultraviolet Voyager spacecraft flyby images in 1986, and near-infrared observations taken from a ground-based Observatoryin 1993. However, no other HST images taken almost every Summer from 1994 up to 2006 have shown such a dark spot.

This indicates that the current dark disturbance probably formed very recently (...)".