Great Red Spot

Thermal images (left) from the ESO's Very Large Telescope, and others in Chile and Hawaii, have shown that the color of Jupiter's Great Red Spot is related to its temperature. Three times bigger than the Earth, the storm's deep red central region is 3–4 degrees warmer than its surroundings

A vast, swirling, oval feature in the equatorial region of Jupiter's atmosphere. Measuring about 14,000 km from north to south and about 25,000 to 40,000 km from east to west (big enough to hold a couple of Earths), it has a color that changes from pale pink or orange to brick red and back again over a timescale of years. This color may be due to the condensation of phosphorus at the cloud tops, to contamination by organic molecules such as nitriles produced by electrical storms, or to material dredged from deeper within Jupiter's atmosphere and then altered by the Sun's radiation.

The Spot is thought to be a hurricane-like disturbance caused and maintained by the Coriolis effect. Infrared observations and the direction of its rotation indicate that the Spot is a high-pressure zone whose cloud tops are significantly higher and colder than the surrounding regions. It has been studied for more than a century and may have been first seen over 300 years ago, its discovery usually attributed to Giovanni Cassini or Robert Hooke in the 16th century.

The Little Red Spot

Little Red Spot, imaged by the Hubble Space Telescope

Little Red Spot (center-left of left image; lower-center of right image) and the Great Red Spot (right image). Hubble Space Telescope images. Credit: NASA/ESA/A Simon-Miller/I de Pater UCB

In early 2006, Jupiter acquired a second prominent red eye which has been nicknamed the "Little Red Spot" (or "Red Spot Junior"), although its official designation is Oval BA. It became a heavily-observed target in 1998 and 2000 when three white storms that had been observed for at least 60 years collided, creating one large white oval. This oval slowly turned to a salmon hue in December 2005, then over the next few weeks became the same color as the Great Red Spot. It is about half the size of its famous partner.

The pictures shown here were taken by the Hubble Space Telescope's Advanced Camera for Surveys on Apr. 8, 2006. Near-infrared measurements indicate that the Little Red Spot may reach high above the main clouds, similar to the Great Red Spot. The images here add evidence to the idea that Jupiter is in the middle of significant climate change. Temperatures at some latitudes could be changing by over 5°C, scientists suggest. Another link to climate is that Red Spot Jr is forming at a latitude of 34° south. Theory has it that this is the where the transfer of heat from the equator to the pole comes to a halt.

Update: Little Red Spot seen by New Horizons probe

The best view yet of the Little Red Spot was provided by the New Horizons spacecraft on Feb. 27, 2007, as it swung past Jupiter on its way to Pluto. From a distance of 3 million km, the probe's Long Range Reconnaissance Imager (LORRI) was able to snap a picture of the Spot at a resolution of 15 km (9 miles) per pixel, which is 10 times better than the resolution provided by the Hubble Space Telescope.

The Little Red Spot imaged by New Horizons on Feb. 27, 2007

From the early LORRI images, it appears that the storm is interacting more with the clouds around it than it was previously, enabling the Little Red Spot to maintain its integrity. The smaller, brighter spot beneath the Little Red Spot is another east-bound storm.

Related category

• PLANETS AND MOONS

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