NASA: Jupiter's Great Red Spot is a 'Sunburn'
We've known for many years that Jupiter's "Great Red Spot" is a persistent anticyclonic storm, but scientists have mostly been at a loss as to the cause of its reddish appearance. Now, a new study from Dr. Kevin Baines of NASA's Jet Propulsion Laboratory may hold the answer, as Baines contends that the new data suggests that the red color is caused by solar ultraviolet light in the planet's atmosphere.
For the study, the researchers tested the hypothesis that UV light from the sun break up chemicals in the atmosphere of Jupiter, producing a reddish substance that gives the Red Spot its distinctive appearance. They applied UV light to several chemicals that are known to be present on Jupiter, including ammonia and acetylene gases, and found that the chemicals broke down into a reddish substance, which seemed to simulate the effect that would occur on Jupiter. When modeling this effect, they found that it was most consistent with a layer of reddish clouds that is limited to the upper atmosphere.
"Our models suggest most of the Great Red Spot is actually pretty bland in color, beneath the upper cloud layer of reddish material," Dr. Baines said. "Under the reddish 'sunburn,' the clouds are probably whitish or grayish."
Dr. Baines also speculated that the increased redness around the Red Spot specifically was the result of its higher altitude compared to the rest of the planet: "The Great Red Spot is extremely tall. It reaches much higher altitudes than clouds elsewhere on Jupiter. Its winds transport ammonia ice particles higher into the atmosphere than usual, where they are exposed to much more of the Sun's UV light. In addition, the vortex nature of the spot confines particles, preventing them from escaping. This causes the redness of the spot's cloud tops to increase beyond what might otherwise be expected."