The Great Red Spot

The year was 1665. Italian astronomer Giovanni Cassini turned his telescope to the planet Jupiter and made an amazing discovery a large “permanent” spot in the southern hemisphere of the giant planet. Cassini and his successors observed the permanent spot regularly until 1712. Only sporadic observations occurred for the next 165 years, but the Great red spot has been systematically observed since 1878.  Despite the been large gap in the record, many astronomers think that the Great Red Spot has existed for more than 340 years, longer than the United States  has been a country. Nevertheless, the Great Red Spot’s definitive existence for the past 130 years makes it the Solar System’s longest-lived storm, Not only is the Great Red Spot long-lived, it is also immense and intense. Approximately three Earths would fit inside Jupiter’s massive storm system. The Great Red Spot towers 8 km (5 miles) over the surrounding cloud tops, nearly the height of Mount Everest. The giant whirlpool is filled with thick, deep clouds and violent turbulence. Like hurricanes on Earth, the Great Red Spot possesses some of the fiercest winds on its home planet, with speeds in excess of 190 m/s (400 mph). Yet unlike Earth’s low-pressure cyclones, Jupiter’s high-pressure vortex spirals in the opposite direction (counterclockwise in the southern hemisphere).
For a moment, just imagine what such a storm would be like on Earth. Hurricane Katrina ravaged the Gulf of Mexico with maximum Winds of 83 m/s (175 mph) and a storm surge of water over 8 m (27 ft) high. The Great Red Spot is five times more energetic than Katrina and would potentially produce a storm surge as tall as a 14-story building (55 m/ 180 ft high). Whereas Katrina lasted for only eight days, the Great Red Spot churns for years and years. The devastation by such a storm would be merciless.

 So what makes this massive storm so long-lived? The Great Red Spot must have a continual source of energy to survive, and this energy comes primarily from two places: Jupiter’s deep interior and nearby smaller vortices. Remarkably, Jupiter’s interior supplies 70% more energy to the cloud tops than the planet receives from the Sun. Like a giant air compressor, gravitational contraction generates intense pressures and heat deep inside the planet. Powerful thunderstorms in Jupiter’s atmosphere channel much of this heat to the cloud tops. A single J ovian thunderstorm releases enough energy to power a typical U.S. household for over 75,000 years.
Because of this large amount of energy, J upiter is a turbulent place. Whorls and eddies abound in the clouds, from relatively small swirling clouds to larger White ovals. But with a mammoth red vortex towering high above other clouds, rapidly spinning as it approaches smaller vortices, the smaller features don’t stand a chance. The Great Red Spot is a voracious eater of smaller eddies. Red Spot Jr. a “small” red spot about half the size of the Great Red Spot, developed from the merger of three White ovals in the late 1990s (it later intensified and turned from white to red for unknown reasons). In 2006, Junior narrowly missed being devoured by its larger cousin. Although Junior escaped for now, the frequent consumption of energetic smaller vortices by the Great Red Spot has probably allowed the giant storm to exist for centuries.
Despite these mergers, the Great Red Spot has been shrinking. Although still enormous, it is only half as large as When observed in the late 19th century. Meanwhile, the speed of its circulating Winds has increased dramatically. These variations are quite puzzling. Are they natural fiuctuations that have occurred many times in the past, with the Great Red Spot repeatedly shrinking and swelling? Or Will Red Spot Jr. continue to intensify and surpass its larger relative as Jupiter’s “permanent” spot? Only time Will tell What lies in store for the longest-lived storm in the Solar System.

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