Are Jupiter's "Red Spots" Under Siege from Violent Climate Change?

Jupiter's atmosphere has a zig-zag pattern of twelve jet streams which make up its signature pastel-toned bands. Earth, by comparison, has only two jet streams. The Great Red Spot (seen in image above from Io) is sandwiched between two of these jets streams, forcing the winds that power those perimeter winds to deflect around the spot.

Spacecraft observations of the way bands of high winds scream past the Red Spot show how the spot -- inaccurately described as a storm -- is actually far calmer at its center than other parts of the Jovian atmosphere. The winds at the center are just 9 or 10 miles per hour, whereas around the perimeter they exceed 200 miles per hour.

A new, third red spot, the Little Red Spot, which is a fraction of the size of the two other red spots, has been observed on Jupiter to the west of the Great Red Spot in the same latitude band of clouds. The visible-light images were taken on May 9 and 10 with Hubble's Wide Field and Planetary Camera.

The new red spot morphed from a white oval-shaped storm to a red color indicating its swirling storm clouds are rising to heights like the clouds of the Great Red Spot. Astronomers surmise that one possible explanation is that the red storm is so powerful it dredges material from deep beneath Jupiter's cloud tops and lifts it to higher altitudes where solar ultraviolet radiation -- via some unknown chemical reaction -- produces the familiar brick color.

Because all three oval storms are bright in near-infrared light, they must be towering above the methane in Jupiter's atmosphere, which absorbs the Sun's infrared light and so looks dark in infrared images.

Turbulence and storms first observed on Jupiter more than two years ago are still raging, as revealed in the latest Hubble and Keck images, which also reveal the change from a rather bland, quiescent band surrounding the Great Red Spot just over a year ago to one of incredible turbulence on both sides of the spot.

The Great Red Spot has persisted for as long as 200 to 350 years, based on early telescopic observations. If the new red spot and the Great Red Spot continue on their courses, they will encounter each other in August, and the small oval will either be absorbed or repelled from the Great Red Spot. Red Spot Jr, which lies between the two other spots, and is at a lower latitude, will pass the Great Red Spot in June.

Jupiter’s cloudtop “surface” is a swirling, constantly changing place that has kept astronomers busy for centuries. The planet’s dark belts and light-hued zones change their appearance and sprout new features frequently. In the past, keen-eyed Jupiter observers eyeballed the comings and goings of new features, but these days much of the monitoring is done with high-quality CCD images obtained by amateur astronomers.

The little red spot (LRS) was first identified by John Rogers, British Astronomical Association’s Jupiter Section director. As Rogers recounts, “This spot appeared last winter while Jupiter was hidden behind the Sun. I noticed it on March 1st in images taken by amateur astronomers Tomio Akutsu in the Philippines and Anthony Wesley in Australia. Such spots in the South Tropical Zone (STrZ) are very rare.”

Since LRS’s discovery, the currents of the STrZ have carried it inexorably toward the Great Red Spot. Jupiter watchers wondered what would happen to the small spot when it encountered the GRS and the adjacent Oval BA (Red Spot Junior). The moment of fate arrived on July 3rd, when the LRS tried to squeeze through the narrow gap between the GRS and adjacent Oval BA like dough through the rollers of a pasta machine.

As of this date, the little spot’s ultimate fate remains unclear. A July 5th image by Japanese amateur Isao Miyazaki and others offer hints that some material from the spot may have survived, perhaps destined to re-form on the other side of the Great Red Spot.

Atmospheric features like the Little Red Spot provide scientists with valuable clues about the dynamics and composition of the Jovian atmosphere.

Currently Jupiter is situated in eastern Sagittarius and visible all night long. The giant planet reaches opposition on July 9th. Under steady viewing conditions, a 4- to 6-inch telescope will show Jupiter’s Great Red Spot quite well, though larger instruments will likely be needed to detect whatever might remain of the LRS.

Posted by Casey Kazan. Image: Jupiter and Giant Red Spot seen from its moon, Io. Vistapro Landscape Imagery Rendered by Jeff Bryant.

Comments

The Great Red Spot. In light of the above article, I now understand that the spot has a boss contour, not a depression.

I respectfully suggest its colour may be caused by light scattering amongst cloud particles whereby all the shorter, visible wavelengths get more scattered than the longest, red -- Tyndall's Effect as known in Physics.

Posted by: Barrie O'Leary | July 10, 2008 at 01:36 AM