Great red spot.

What Is The Great Red Spot?

The Great Red Spot is an enormous storm system on Jupiter that has been raging for hundreds of years. Located in Jupiter’s Southern Hemisphere, this hurricane-like storm contains winds twice as fast as the fastest hurricane-force winds on Earth. It is oval-shaped and red in appearance. The red color of the storm is a subject of discussion in astronomy. The most popular theory available right now states that the products created by ultraviolet irradiation of ammonia coupled with how high the storm is within the atmosphere are to blame for the red color. The first recorded sighting of the Great Red Spot was in 1831 by astronomer Samuel Heinrich Schwabe. This ages the storm to around 200 years but it could be much older. Some theorize that astronomer Gian Domenico Cassini saw it as early as 1665 because of his writings on a “permanent storm”. However, this cannot be proven. 

How Is The Great Red Spot So Old?

Great Red Spot by Voyager
Image of the Great Red Spot taken by the Voyager 1 spacecraft. Image credit: NASA

Jupiter is a gas giant, which means that the planet possesses no solid surface. Instead, Jupiter is made up of a thick gaseous surface over a theorized liquid layer. Jupiter’s surface also shows stripes of different colors, known as zonal winds. Zonal winds are parallel to the equator with winds of differing intensity. The Great Red spot is located between two zonal winds that are moving in opposition to each other. The band above the great red spot moves eastwards while the band below moves westward. This could be one of the factors that contribute to the longevity of the storm because the differing directions of the wind add energy to the storm. Another factor could be the lack of a solid surface. Hurricanes on Earth break apart when they hit solid land. Thus, the Great Red Spot continues to flourish without anything solid on Jupiter’s surface to dissipate the energy within the storm. 

How Big Is The Great Red Spot?

Great Red Spot by Juno
Image of the Great Red Spot taken by the Juno spacecraft. Image credit: NASA

Over time, the Great Red Spot grows and shrinks. However, it has not grown for some time. At one time, the storm was three times the size of Earth. Now the Great Red Spot is only 1.3 times the size of Earth. The reason for this massive difference in size is unknown. Astronomers believe that an unnamed process within the gas giant could be stealing energy from the storm, yet they do not know what this process could be. For now, the Great Red Spot is one of the solar system's most intriguing mysteries. 

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