We know that Jupiter's Great Red Spot is red. Its color is right there in the name. However, why is it red? A team of NASA scientists recently found out.
Previous theories about the reddish color of Jupiter's Great Red Spot suggested that the color comes from chemicals beneath Jupiter's clouds, with certain chemicals forming lower in Jupiter's atmosphere and then rising to the top of the spot.
However, after studying new data from NASA's Cassini spacecraft, along with laboratory experiments, scientists think that the red in the Red Spot comes from sunlight hitting chemicals higher up in Jupiter's upper atmosphere.
After studying Cassini's data, researchers used ultraviolet light to mimic sunlight, and blasted it at two gases known to exist on Jupiter: ammonia and acetylene. The result was a red material that matched Cassini's observations of Jupiter's Great Red Spot.
"Our models suggest most of the Great Red Spot is actually pretty bland in color, beneath the upper cloud layer of reddish material," says Kevin Baines, a Cassini team scientist. "Under the reddish 'sunburn' the clouds are probably whitish or grayish."
The Great Red Spot is actually a massive storm on the surface of Jupiter. It's so big that three Earths could easily fit inside it. Discovered in the 1600s, the storm reaches high into Jupiter's upper atmosphere.
"The Great Red Spot is extremely tall," Baines says. "It reaches much higher altitudes than clouds elsewhere on Jupiter."
This high altitude is why the Great Red Spot's color is so intense: the storm's winds bring ammonia ice particles into the upper atmosphere, exposing it to more sunlight. Because the storm is spinning, similar to a hurricane, the ammonia particles can't escape. This creates a constant red color at the top of the storm.
So why is the Great Red Spot's color so important? Jupiter only has a few elements, with its body mostly formed of hydrogen and helium. By examining the colors on the planet's surface, scientists can identify those elements and get a better idea of the planet's chemical composition.
Jupiter displays a variety of similar shades across its surface: oranges, browns and other shades of red. These colors suggest areas with thinner and higher clouds, which lets us see deeper into Jupiter's atmosphere.
The Great Red Spot, though, stands out as one of Jupiter's more mysterious features. Jupiter has no land mass, so a storm of that magnitude should have disappeared quickly in such a turbulent atmosphere. However, the Great Red Spot is still there, although recent measurements show that it's possibly shrinking.
[Photo Credit: NASA, ESA, A. Simon-Miller (Goddard Space Flight Center), I. de Pater, M. Wong (UC Berkeley)]
