This image shows how the Great Cold Spot changes dramatically in shape and size on different days. |
University of Leicester

A new massive storm has been spotted in Jupiter’s upper atmosphere, and it’s considerably cooler than its blistering surroundings.

With its massive size, enormous magnetic field and giant storms, Jupiter has been called a planet of extremes. Now, a new storm has been spotted at Jupiter, and this one is even more volatile and extreme than the famous “Great Red Spot.”

It’s also much colder.

University of Leicester

Nicknamed the “Great Cold Spot,” this storm spans 15,000 miles (24,000 kilometers) across and 7,500 miles (12,000 kilometers) wide. Located in Jupiter’s upper atmosphere, the storm is considerably cooler than its blistering surroundings, and researchers think it was formed by energy from Jupiter’s polar aurora.

Although the Great Cold Spot was only recently discovered, archival data reveals that the storm has actually been around for at least 15 years, and likely much longer.

“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,” said Tom Stallard from the University of Leicester in the UK, lead author of the new paper, in a press release. “That suggests that it continually reforms itself, and as a result it might be as old as the aurorae that form it — perhaps many thousands of years old.”

Astronomers used an infrared instrument on the Very Large Telescope (VLT) in Chile along with images from NASA’s InfraRed Telescope Facility in Hawaii that were taken between 1995 and 2000. They were able to map the mean temperature and density of Jupiter’s atmosphere over several years, which revealed the presence of a dark ‘cooler’ area in the hot environment of Jupiter’s upper atmosphere. The temperatures there usually range from 700 Kelvin (426 degrees Celsius) to 1000 Kelvin (726 degrees Celsius). The region of the Great Cold Spot registered at least 200°K (100°C) cooler.

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Jupiter’s giant, spectacular polar aurorae are created by the effects of the magnetic field of the planet combining with gases from the volcanic moon Io. The aurora drives energy into the atmosphere in the form of heat flowing around the planet. The researchers think this flow creates a vortex of cooler gasses in the uppermost layer of Jupiter’s atmosphere — called the thermosphere — creating the Great Cold Spot.

This is the first direct evidence of a sustained weather system generated by polar aurorae on any planet, and this is the first time a weather feature in Jupiter’s upper atmosphere has been observed away from the planet’s bright aurorae. Although Stallard and his team said they aren’t sure yet what drives the continuous Great Cold Spot, a sustained cooling is very likely to create a vortex similar to the Great Red Spot.

“The detection of the Great Cold Spot was a real surprise to us,” Stallard said, “but there are indications that other features might also exist in Jupiter’s upper atmosphere. Our next step will be to look for other features in the upper atmosphere, as well as investigating the Great Cold Spot itself in more detail.”

Stallard and his team will be taking advantage of the Juno spacecraft currently in orbit around Jupiter, particularly the observations of Jupiter’s aurora and upper atmosphere by the Jovian Infrared Auroral Mapper (JIRAM) instrument.

Some data from JIRAM have already been released, which Stallard said are providing a wealth of new information about Jupiter.

“When combined with our ongoing campaign of observations using telescopes on Earth, we hope to gain a much better understanding of this weather system in the next few years,” he said.