The Great Red Spot has been seen continuously since at least 1830, though it may have developed earlier. In recent decades, it has been shrinking in size; in April of this year, it measured 10,159 miles (16,350km) across, or about 1.3 Earth diameters. Its winds have been clocked at 400 miles per hour (640km/h), though its center is calm, like the eye of an earthly hurricane. Recent experiments suggest that the storms red color is caused by a reaction in Jupiters upper atmosphere when energetic ultraviolet photons in sunlight hit ammonia and acetylene gas.

For hundreds of years scientists have been observing, wondering and theorizing about Jupiter's Great Red Spot. Now we have the best pictures ever of this iconic storm, said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. Although he added that it will take time to sort through and analyze the influx of new data, the details Juno is returning are vital to understanding the storms dynamics, both past and present.

The July 10 flyby was Junos seventh close approach to the planet; in total, it will orbit Jupiter 37 times, with the closest pass bringing the spacecraft within about 2,100 miles (3,400km) of the cloud tops. At mission's end in 2018, Juno will plunge into the planet's atmosphere, just like the Cassini mission currently orbiting Saturn.

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Juno gets up close and personal with Jupiter's Great Red Spot ... - Astronomy Magazine