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13 April 2017

Inside Jupiter’s ‘Great Cold Spot’

Img: University of Leicester
The Great Red Spot of Jupiter is a well-known phenomenon, confirmed to have been continually observed for 187 years, since the year 1830. It is actually reported that early astronomers were observing the storm as early as 1665, which would mean that the same storm has been swirling through the gas giant’s atmosphere for more than 350 years. The storm stretches wide enough to cover the Earth twice over, and consists of deadly winds travelling at approximately 400mph. The Great Red Spot is undoubtedly extreme, but it is not the only long-spanning and abnormal weather pattern present in Jupiter’s gaseous atmosphere.

I refer now to a recently discovered storm known as the Great Cold Spot, which covers an area of around 15,000 miles across by 7,500 miles wide and is believed to be much more severe and volatile than its more-famous red equivalent, according to a new study from  the University of Leicester. It also sits at a significantly lower temperature, earning the weather pattern its rather apt nickname.

Believed by researchers to be formed and fuelled by energy from Jupiter’s polar aurora, the storm has been active for at least 15 years, as confirmed by archival data. The researchers further believe that due to the way in which the storm continually reforms itself, it may in fact be much older than that.

“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,” says Tom Stallard of the University of Leicester, who served as lead author of the new paper.

“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.”

So just how cold is the Great Cold Spot? Well, to answer that we have to look back to its discovery.

The storm was discovered via use of an infrared instrument on Chile’s rather appropriately yet unimaginatively named Very Large Telescope (VLT), alongside images taken by NASA’s Infrared Telescope Facility in Hawaii between the years of 1995 and 2000. These observations allowed the research team to effectively map the mean temperature and density of Jupiter’s atmosphere over a period of several years. This mapping revealed the presence of a much cooler dark area within the upper atmosphere, later identified as the Great Cold Spot. The average temperature within the upper atmosphere ranges between 426°C and 726°C; temperatures within the Great Cold Spot sit at least 100°C cooler than this average.

The aurorae suspected to be responsible for the Great Cold Spot are themselves created as a result of the planet’s magnetic field interacting with gases from the volcanic moon Io. This creates a vortex off cooler gases in the upper layers of the atmosphere which culminate in the Great Cold Spot. According to Seeker.com, this is the first direct evidence of a sustained weather system generated by polar aurorae on any planet.

“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.”


Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.