Astronomers get a closer look at Jupiter's Great Red Spot

Posted by Emma Woollacott

New thermal images from ESO's Very Large Telescope (VLT) are allowing astronomers to take a detailed look at the solar system's largest storm.

They show that the reddest part of the Great Red Spot corresponds to a warm core within the otherwise cold storm system, which averages about -160 degrees Celsius. Images show dark lanes at the edge of the storm where gases are dropping into deeper areas.   

"This is our first detailed look inside the biggest storm of the solar system," says team leader Glenn Orton. "We once thought the Great Red Spot was a plain old oval without much structure, but these new results show that it is, in fact, extremely complicated."

The Great Red Spot has been intriguing stargazers for hundreds of years, with continuous observations of its current shape dating back to the 19th century.

The astronomers mapped the temperature, aerosols and ammonia within and surrounding the storm. Each gives more information on how the weather and circulation patterns change in space and time. They show the storm is incredibly stable despite turbulence, upheavals and close encounters with other anticyclones.

"One of the most intriguing findings shows the most intense orange-red central part of the spot is about three to four degrees warmer than the environment around it," says lead author Leigh Fletcher.

This is enough to allow the storm circulation, usually counter-clockwise, to shift to a weak clockwise circulation in the very middle of the storm. Not only that, but on other parts of Jupiter, the temperature change is enough to alter wind velocities and affect cloud patterns in the belts and zones.

"This is the first time we can say that there's an intimate link between environmental conditions — temperature, winds, pressure and composition — and the actual colour of the Great Red Spot," says Fletcher.

"Although we can speculate, we still don't know for sure which chemicals or processes are causing that deep red colour, but we do know now that it is related to changes in the environmental conditions right in the heart of the storm."