It’s big enough you could toss Earth in there and still have a little room. Located in the thin high-altitude thermosphere, the spot likely has Jupiter’s northern lights to thank for creating it.
A team of astronomers used the Very Large Telescope (VLT) array in Chile to observe the spot. Using the CRIRES instrument on the VLT to observe spectral emissions of H3+ (an ion of hydrogen seen in large quantities in the atmosphere), they compared the new data with old data collected between 1995-2000 by NASA’s InfraRed Telescope Facility.
They found a dark, cold area surrounded by Jupiter’s hot upper atmosphere.
Credit: University of Leicester
You can see the darker area rotate into view across the series of images. You’re looking at an area that is about 200 Kelvin cooler (about 100 degrees F) than the surrounding atmosphere. The warm atmosphere temperatures range between 700K (800 degrees F) and 1000K (1,340 degrees F).
Dr. Tom Stallard, the lead author of the study, explains what we are looking at. “This is the first time any weather feature in Jupiter’s atmosphere has been observed away from the planet’s bright aurorae.”
Dubbed ‘The Great Cold Spot,’ the similarities between the Great Red Spot and Cold Spot stop at spot. Both are persistent, but the Cold Spot’s shape can change quickly. We’re talking days to weeks, not years.
But the feature always pops up in more than 15 years of data. “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.”
Ok, how does it form? Astronomers can’t give a definitive answer yet. They’re hoping NASA’s Juno spacecraft currently circling the gas giant will help shed some light on it. But here’s what they think is going on.
Cold spot changing quickly over a span of days. Credit: University of Leicester
The Great Cold Spot is thought to be caused by the effects of the magnetic field of the planet, with the massive planet’s spectacular polar aurorae driving energy into the atmosphere in the form of heat flowing around the planet.
This creates a region of cooling in the thermosphere, the boundary layer between the underlying atmosphere and the vacuum of space. Although we can’t be sure what drives this weather feature, a sustained cooling is very likely to drive a vortex similar to the Great Red Spot.
The Great Cold Spot might have some company too. Besides this cool surprise, Stallard and his colleagues observed hints of other features potentially lurking in Jupiter’s upper atmosphere.
Who knows what other weather features are waiting to be discovered. Juno is in a perfect position to help Stallard learn more about the mysteries of our Solar System’s largest planet. And take plenty of stunning pictures.