Are Jupiter’s Massive Belt & Great Red Spot (Three Times the Size of Earth) Changing Colors?



Jupiter's massive, and recently new, white band isn't the only change on the big, gas giant. At the same time, Jupiter's Great Red Spot became a darker red color. said Glenn Orton, a research scientist at JPL The color of the spot – a giant storm on Jupiter that is three times the size of Earth and a century or more old – will likely brighten a bit again as the South Equatorial Belt changes.

The South Equatorial Belt underwent a slight brightening, known as a “fade,” just as
NASA's New Horizons spacecraft was flying by on its way to Pluto in 2007. Then there
was a rapid “revival” of its usual dark color three to four months later. The last full fade
and revival was a double-header event, starting with a fade in 1989, revival in 1990, then
another fade and revival in 1993. Similar fades and revivals have been captured visually
and photographically back to the early 20th century, and they are likely to be a long-term
phenomenon in Jupiter’s atmosphere.

Earlier this year, amateur astronomers noticed that a longstanding dark-brown stripe,
known as the South Equatorial Belt, just south of Jupiter's equator, had turned white. In
early November, amateur astronomer Christopher Go of Cebu City, Philippines, saw an
unusually bright spot in the white area that was once the dark stripe. This phenomenon
piqued the interest of scientists at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.,
and elsewhere.

After follow-up observations in Hawaii with NASA's Infrared Telescope Facility, the
W.M. Keck Observatory and the Gemini Observatory telescope, scientists now believe
the vanished dark stripe is making a comeback.

"The reason Jupiter seemed to ‘lose’ this band – camouflaging itself among the
surrounding white bands – is that the usual downwelling winds that are dry and keep the
region clear of clouds died down," said Orton. "One of the things we were looking for in the infrared was evidence that the darker material emerging to the west of the bright spot was actually the start of clearing in the cloud deck, and that is precisely what we saw."

This white cloud deck is made up of white ammonia ice. When the white clouds float at a
higher altitude, they obscure the missing brown material, which floats at a lower altitude.
Every few decades or so, the South Equatorial Belt turns completely white for perhaps
one to three years, an event that has puzzled scientists for decades. This extreme change
in appearance has only been seen with the South Equatorial Belt, making it unique to
Jupiter and the entire solar system.

Scientists are particularly interested in observing this latest event because it’s the first
time they've been able to use modern instruments to determine the details of the chemical
and dynamical changes of this phenomenon. Observing this event carefully may help to
refine the scientific questions to be posed by NASA’s Juno spacecraft, due to arrive at
Jupiter in 2016, and a larger, proposed mission to orbit Jupiter and explore its satellite
Europa after 2020.

The image above is a composite of three color images taken on Nov. 18, 2010, by the Gemini North telescope in Hawaii. The composite image shows a belt that had previously vanished in Jupiter's atmosphere is now reappearing. .

The three images used to make the composite were taken at three different parts of the infrared spectrum – 2.12 microns (blue), 1.69 microns (yellow) and 4.68 microns (red). At 1.69 microns, scientists see sunlight reflected from Jupiter's main cloud deck – the same clouds they see in visible light. At 2.12 microns, scientists see sunlight reflected from higher-altitude particles well above the main deck. At 4.68 microns, scientists see thermal emission arising from the tops of Jupiter's clouds, with the hottest emissions coming from the deepest atmosphere and signifying regions with minimal overlying cloud cover.

The region just to the left of the center, inside the white box, shows the region of the South Equatorial Belt with an unusually bright spot, or outbreak. One thing scientists were looking for in infrared was evidence that the darker material emerging to the west of the bright spot was the start of the clearing of the cloud deck. The particles lofted by the initial outbreak are easily identified in yellow as high-altitude particles at the upper right, with a second outbreak to the lower left. In the coming weeks, further outbreaks are expected to take place to the west (left) of those seen in this image, and the clear atmospheric regions will begin to fill this latitude band at the same time as the dark brown color typical of this region returns.

The event also signifies another close collaboration between professional and amateur
astronomers. The amateurs, located worldwide, are often well equipped with
instrumentation and are able to track the rapid developments of planets in the solar
system.  These amateurs are collaborating with professionals to pursue further studies of
the changes that are of great value to scientists and researchers everywhere.

"I was fortunate to catch the outburst," said Christopher Go, referring to the first signs
that the band was coming back. "I had a meeting that evening and it went late. I caught
the outburst just in time as it was rising. Had I imaged earlier, I would not have caught
it," he said. Go, who also conducts in the physics department at the University of San
Carlos, Cebu City, Philippines, witnessed the disappearance of the stripe earlier this year,
and in 2007 he was the first to catch the stripe's return. "I was able to catch it early this
time around because I knew exactly what to look for."

Jason McManus via NASA

Image credit: NASA/JPL/UH/NIRI/Gemini


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