Jupiter’s giant cyclone revealed

Infrared and visible light images of Jupiter's Great Red Spot

Infrared (left) and visible wavelength images of Jupiter's Great Red Spot, a huge cyclone that has been raging in the planet's atmosphere for at least 400 years.

New thermal images from powerful ground-based telescopes show swirls of warmer air and cooler regions never seen before within Jupiter’s Great Red Spot, giving scientists their first detailed interior weather map of the giant storm system.

The observations reveal that the reddest colour of the Great Red Spot corresponds to a warm core within the otherwise cold storm system, and images show dark lanes at the edge of the storm where gases are descending into the deeper regions of the planet.

These types of data, detailed in a paper appearing in the journal Icarus, give scientists a sense of the circulation patterns within the Solar System’s best-known storm system.

“This is our first detailed look inside the biggest storm of the Solar System,” said Glenn Orton, a senior research scientist at NASA’s Jet Propulsion Laboratory, who was one of the authors of the paper.

“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.”

A multi-telescope effort

Skygazers have been observing the Great Red Spot in one form or another for hundreds of years, with continuous observations of its current shape dating back to the 19th century. The spot, which is a cold region averaging about minus 163 degrees Celsius, is so wide about three Earths could fit inside its boundaries.

Jupiter, showing it's Great Red Spot

Jupiter, showing it's Great Red Spot

The thermal images obtained by giant 8-metre telescopes used for this study—the European Southern Observatory’s Very Large Telescope in Chile, the Gemini Observatory telescope in Chile and the National Astronomical Observatory of Japan’s Subaru telescope in Hawaii—have provided an unprecedented level of resolution and extended the coverage provided by NASA’s Galileo spacecraft in the late 1990s.

Together with observations of the deep cloud structure by the 3-metre NASA Infrared Telescope Facility in Hawaii, the level of thermal detail observed from these giant observatories is comparable to visible-light images from NASA’s Hubble Space Telescope for the first time.

Still a mystery

One of the most intriguing findings shows the most intense orange-red central part of the spot is about 3 to 4 degrees Celsius warmer than the environment around it, said Leigh Fletcher, the lead author of the paper, who completed much of the research as a postdoctoral fellow at JPL and is currently a fellow at the University of Oxford in England.

This temperature differential might not seem like a lot, but it 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,” Fletcher said.

“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.”

Unlocking the secrets of Jupiter’s giant storm systems will be one of the targets for infrared spacecraft observations from future missions including NASA’s Juno mission.

Adapted from information issued by NASA / ESO / Gemini Observatory / NAOJ.

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