This 4-panel frame shows a section of Jupiter's North Equatorial Belt viewed by Cassini at 4 different wavelengths on November 27, when the resolution had improved to 192 km/pixel, surpassing the Hubble Space Telescope Wide Field Camera in resolving power. The images have been contrast-enhanced for the purpose of illustration. The upper panel is an image taken in the near-infrared at a wavelength inaccessible to the human eye. The gases in the atmosphere are relatively non-absorbing, allowing sunlight to penetrate deeply into the atmosphere and be reflected back out, thus giving us a direct view of the deeper regions of the troposphere. (On Earth, the troposphere is the portion of the atmosphere closest to the surface, in which most of the atmospheric water vapor resides.)
The second panel is taken in the blue at shorter wavelengths detected by the human eye. At these wavelengths, gases in the atmosphere scatter a modest amount of sunlight, so the clouds we see tend to be at somewhat higher altitudes than in the uppermost panel.
The third panel shows near-infrared reflected sunlight at a wavelength where the gas methane, an important constituent of Jupiter's atmosphere, absorbs strongly. In this image, dark places are locations of strong absorption (i.e., regions without high-level clouds and consequently large amounts of methane accessible to sunlight), and bright regions are locations with high (upper troposphere) clouds shielding the methane below.
The bottom-most panel is an image taken in the ultraviolet. At these very short wavelengths, the clear atmosphere scatters sunlight, and stratospheric hazes absorb sunlight, both very efficiently, making it difficult to see into the troposphere at all. So bright regions are generally free of high stratospheric hazes.
The fascinating aspect of these 4 images is the small bright spot that can be seen in the center of each one. Bright spots similar to this were seen in turbulent regions by the Galileo cameras, and they appear to be very energetic convective storms that move heat from the interior of Jupiter to higher altitudes. These storms are expected to penetrate to great heights, and so it is not surprising to see the storm in the first three images, which probe atmospheric altitudes from the lower to the upper troposphere. What is surprising is the appearance of the spot in the ultraviolet image. This may in fact be a `monster' thunderstorm, penetrating all the way into the stratosphere, as do some summer thunderstorms in the midwestern United States. Higher resolution, time-lapse images to be captured in the coming weeks will shed more light on these spectacular features.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.