It's official: Jupiter is big enough to be home to not just one, but two great spots. University of Leicester astronomers report that they have discovered what they call the "Great Cold Spot" that is almost as big as the gas giant's famed "Great Red Spot." But this newfound spot is set apart not only by how chilly it is compared to its surroundings, but by the fact that it is created by the planet's highly energetic auroras.
The dark, cold spot is in Jupiter's thin thermosphere, which separates the vacuum of space from the planet's thicker atmosphere below, and has been observed to be as large as 24,000 km (14,913 mi) in longitude by 12,000 km (7,456 mi) in latitude. It's also 20 to 30 percent cooler than the surrounding atmosphere, which roils between 426° C (799° F) and 726° C (1,339° F).
Perhaps ironically, the Great Red Spot has been suspected of driving the planet's mysterious heat.
"The Great Cold Spot is much more volatile than the slowly changing Great Red Spot, changing dramatically in shape and size over only a few days and weeks, but it has re-appeared for as long as we have data to search for it, for over 15 years," explains professor Dr. Tom Stallard, a lead author of
He adds that the cold spot may go through cycles of breaking down and reforming itself, perhaps stretching back over many thousands of years.
Unlike auroras on Earth that are largely driven by activity from the Sun, Jupiter's are dominated by gases from the volcanic moon Io. The Jovian auroras drive heat energy into the planet's atmosphere, creating an area of cooling in the higher altitude thermosphere via processes that are not fully understood, but which seem to drive a vortex similar to the one seen at the Great Red Spot.
"The detection of the Great Cold Spot was a real surprise to us, but there are indications that other features might also exist in Jupiter's upper atmosphere," Stallard says.
His team plans to look for more such features in the highest reaches of the gas giant's atmosphere and get a better look at the cold spot, probably with the help of data from the Juno spacecraft currently orbiting Jupiter and telescopes on Earth.
The team's study published this week in Geophysical Research Letters and the researchers explain the discovery in the video below.
Source: University of Leicester