Article Posted on : - Jul 07, 2011

An image of Saturn taken in December 2010 by the Cassini spacecraft shows a storm with a latitudinal and longitudinal extent of 10,000 km and 17,000 km, respectively. Photo: NASA?JPL

LONDON (PTI): For the first time, scientists have captured in unprecedented detail a massive storm raging on Saturn which is producing lightning bolts 10,000 times stronger than those on Earth.

The storm has caused a "Great White Spot" on the planet which is visible from Earth.

Great White Spots, which are ten times larger than the regular storms, are rarer and occur about once per Saturnian year (or 29.5 years on Earth), the Daily Telegraph reported.

According to researchers, the storm has a latitude and longitude of 6,200 and 10,500 miles respectively -- meaning it would spread across half of the Earth.

Observations from the Cassini spacecraft combined with images from ground-based telescopes, showed that the electric spectacle is producing a tempest so intense the flashes are occurring at the rate of up to ten times a second, according to the researchers who reported their findings in two papers in the journal Nature.

This outburst, they said, began last December as Cassini orbited the usually calm ringed planet while a network of ground-based observers also monitored the storm's evolution.

Professor Agustin Sanchez-Lavega of the School of Engineering of Bilbao and colleagues said: "It is only the sixth time the once-in-a-generation phenomenon -- which occurs as spring comes to the 87,000 mile wide planet's northern hemisphere -- has been spotted since 1876.

In a second study, Dr Georg Fischer of the Austrian Academy of Sciences in Graz and colleagues said: "The visible plume consists of high-altitude clouds that overshoot the outermost ammonia cloud layer owing to strong vertical convection, as is typical for thunderstorms.

"The flash rates of this storm are about an order of magnitude higher than previous ones, and peak rates larger than ten per second were recorded."

"Unlike storms on Earth, the total power of this storm is comparable to Saturn's total emitted power," the researchers said, adding that appearance of such storms in the northern hemisphere could be related to the change of seasons.

Physicist Professor Peter Read, of Oxford University, who reviewed the papers said they present "some of the most detailed observations so far of such a dramatic event".

"These observations reveal with great clarity that the GWS comprises a massive complex of convective thunderstorms, upwelling heat energy and moisture from levels deep within Saturn's atmosphere, accompanied by huge and almost continuous lightning discharges," he said.

"It will be a major challenge to the next generation of atmospheric models to predict when (and where) storm clouds will next appear to brood over Saturn's normally bland and hazy face," he added.