The polar vortex and hot spot — believed to contain the highest measured temperatures on Saturn — are described in a paper that appears in the Feb. 4 issue of Science magazine.

A polar vortex is a persistent, large-scale weather pattern, much like a jet stream on Earth. On our planet, the Arctic polar vortex typically blasts cold air over the northern plains. The Antarctic polar vortex is responsible for trapping air and creating unusual phenomena such as the "ozone hole."

The polar vortexes on Earth, Jupiter, Mars and Venus are colder than their surroundings. But the new images from the W. M. Keck Observatory show the first evidence of a polar vortex at much warmer temperatures, and the compact hot spot at the pole itself is quite unusual, scientists said.

"There is nothing like this compact warm cap in the Earth's atmosphere," said Glenn S. Orton of the Jet Propulsion Laboratory in Pasadena, Calif.

Scientists already know Saturn's south pole is warm. It's been been exposed to 15 years of continuous sunlight during its slow orbit around the sun. What they didn't expect was both the distinct boundary of a warm polar vortex some 30 degrees latitude from the southern pole and the very hot tip at the pole.

The team of scientists said the images are the sharpest thermal views of Saturn ever taken from the ground. The twin Keck Telescopes are the world's largest optical and infrared telescopes.

More details may be coming from the infrared spectrometer on the Cassini spacecraft currently orbiting Saturn, they said.