University of Leicester astronomers discover Great Cold Spot on Jupiter 11 April 2017

A second Great Spot has been discovered on Jupiter by University of Leicester astronomers, rivalling the scale of the planet’s famous Great Red Spot and created by the powerful energies exerted by the great planet’s polar aurorae.

The ‘Great Cold Spot’ is comparable in size to the famous Great Red Spot, measuring up to 24,000 km in longitude and 12,000 km in latitude. The phenomenon, only recently observed using the CRIRES instrument on the Very Large Telescope (VLT), may have existed for thousands of years.

The results are published today (11 April) in Geophysical Research Letters.

Dr Tom Stallard, Associate Professor in Planetary Astronomy and lead author of the study, said: “This is the first time any weather feature in Jupiter's upper atmosphere has been observed away from the planet's bright aurorae.

“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. 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.”

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.

Watch an interview with Dr Tom Stallard about the 'Great Red Spot':