Light-colored bands parallel to Jupiter's Equator are cooler regions containing ammonia clouds, which reflect more light than the planet as a whole. Dark-colored bands are warmer regions without ammonia clouds, which reflect less light. Lighter bands rotate eastward relative to average planetary rotation, while darker bands rotate westwards. The dark spot to the left of center is the shadow of Io (producing a total eclipse of the Sun in the region covered by the shadow)

     Although astronomers still don't entirely understand the dynamics of the Great Red Spot, a gigantic storm visible since the beginning of detailed telescopic observations of the planet more than 300 years ago, they recently had a chance to learn more about its nature by observing the birth of a similar, smaller spot. "Red Spot Junior", which is about the same diameter as the Earth, is shown in this April 2006 Hubble Space Telescope false-color image, down and to the left of the Great Red Spot, which is about the same size as the entire surface of the Earth. The junior member of the pair was formed earlier in 2006, when two smaller whitish storms merged. The larger stronger storm that resulted soon changed color, to match its larger predecessor. Presumably the reddish color results from materials swept up from the depths of Jupiter's atmosphere by the more powerful winds in the large storms, while smaller whiter storms don't have strong enough winds to reach deep enough into the atmosphere to stir up the coloring materials. What those materials are and why they are found only at greater depths remains a mystery. (NASA, ESA, A. Simon-Miller (Goddard Space Flight Center), I. de Pater, M. Wong (UC Berkeley), apod060505)

     Infrared image taken in mid-July 2006, as the Great Red Spot and Oval BA ("Red Spot Jr") passed each other. In this false-color image, white represents higher clouds, blue deeper clouds, and red the deepest. The two Red Spots, having the highest clouds, are therefore shown in white instead of their actual reddish tint. It now appears that the two storms will not merge, but will gradually separate as the differing rotation rates of their circulation systems carry them around the planet relative to each other. In a few years, if the smaller spot survives that long, they will pass each other again. (Travis Rector (U. Alaska), Chad Trujillo (Caltech et al., Gemini Obs., AURA, NSF, apod060725)

     An ultraviolet image of Jupiter's aurora borealis taken with the Hubble Space Telescope. Unlike the Earth's aurorae, Jupiter's aurorae are strongly affected by the interaction of its magnetic field with its large moons. Flux tubes (regions of greater than normal magnetic field strengths) connect the planet to its moons, intensifying the auroral activity in specific locations. In this image, the bright streak on the far left is caused by Io's interaction with Jupiter, and the dots below center and to the right of that are caused by interactions with Ganymede (on the left) and Europa (on the right). (John T. Clarke (U. Michigan), ESA, NASA, apod001219)

     A core of ice and rock (in brown) of unknown size and mass (about the size of the Earth, but around 10 to 20 Earth masses) is probably crushed to a solid state by the immense pressures inside the planet. Overlying that is a large region (shown in dark gray) of hydrogen so compressed that it behaves like a molten metal. The outermost part of the planet (shown in lighter gray) is hydrogen compressed to the density of a liquid, which merges into the atmosphere (the lightest gray) a few hundred miles beneath the clouds visible from space. (modified version of Lunar and Planetary Institute image; NASA)