A dramatic new time-lapse movie (only 5-6 August 1998 shown here) by NASA's Hubble Space Telescope shows for the first time seasonal changes on the planet. Once considered one of the blander-looking planets, Uranus is now revealed as a dynamic world with the brightest clouds in the outer Solar System and a fragile ring system that wobbles like an unbalanced wagon wheel. The clouds are probably made of crystals of methane, which condense as warm bubbles of gas well up from deep in the atmosphere of Uranus.

Karkoschka, Hammel and other investigators used Hubble from 1994 through 1998 to take images of Uranus in both visible and near-infrared light.

The Northern Hemisphere of Uranus is just now coming out of the grip of its decades-long winter. As the sunlight reaches some latitudes, it warms the atmosphere. This appears to be causing the atmosphere to come out of a frigid hibernation and stir back to life. Uranus does not have a solid surface, but is instead a ball of mostly hydrogen and helium. Absorption of red light by methane in the atmosphere gives the planet its cyan colour.