This NASA Hubble Space Telescope (HST) image of Saturn shows a rare storm that appears as a white arrowhead-shaped feature near the planet’s equator. The east-west extent of this storm is equal to the diameter of Earth. The storm of condensed ammonia ice crystals was discovered in September 1994, and is changed very little in this view taken by HST on December 1, 1994. Such upwellings in Saturn’s atmosphere have been observed only three times during the past two centuries, and scientists are still trying to explain its somewhat periodic reappearance.
Hubble Space Telescope image (Press Release PRC-94-53).