Jupiter's Red Spot is Like Planet 'Sunburn'

The iconic Great Red Spot of Jupiter is arguably the most recognizable characteristic of our solar system's largest planet. However, the mystery of what this massive blush really is remains unsolved. Now, researchers believe they have finally determined the nature of this spot and the process behind it, arguing that it's not really like a blush, but more like gas giant sunburn.

That's at least according to Kevin Baines, a Cassini team scientist based at NASA's Jet Propulsion Laboratory, who plans to present some stunning lab results at the American Astronomical Society's Division for Planetary Science Meeting in Tucson, Arizona.

Past theories about the Great Red Spot (GRS) have suggested that Jupiter is actually the same vibrant red throughout the whole of the planet, but only in atmospheric layers beneath the pale oranges and whites that we see. The spot then would be a chemical build-up of these red atmospheric ingredients, visible at the point where an intense and anticyclonic vortex continues to occur alongside the planet's lesser storms.

However, based off data from a Cassini flyby and lab experimentation in December 2000, Baines and his colleagues Bob Carlson and Tom Momary are now suggesting that, beneath the planet's ruddy-red, the GRS is actually pretty bland in color.

"Under the reddish 'sunburn' the clouds are probably whitish or grayish," Baines said in a statement.

The researchers determined this after recreating a close approximation of Jupiter's atmosphere in a lab. They then blasted chemicals - primarily ammonia and acetylene gases - with ultraviolet light to simulate how the Sun beats down on the GRS clouds. After a bit of time, the resulting chemical breakdown produced a reddish material, but only at the very outer layers of the simulated cloud. (Scroll to read on...)

If an upwelling of redder chemicals was actually occurring at the vortex, like the other leading theory suggests, the researchers argue that the GRS would be redder still, as this "sunburn" effect would still be occurring.

However, this doesn't explain why the whole of Jupiter, which sees regular Sun exposure in its 10-hour day, is not entirely red. The researchers suggest that altitude is key.

"The Great Red Spot is extremely tall," Baines said. "It reaches much higher altitudes than clouds elsewhere on Jupiter."

Baines and his colleagues suggest that intense winds of the massive vortex - twice the size of Earth - transport ammonia ice particles higher into the atmosphere than usual, where they are exposed to much more of the Sun's ultraviolet light. These reddened particles are then confined by the ever-rising winds, making them visible from space.