As Cassini nears its rendezvous with Saturn, new detail in the banded clouds of the planet's atmosphere are becoming visible. Cassini took this narrow angle camera image on April 16, 2004 when it was 38.5 million kilometers (23.9 million miles) from Saturn. The image scale is approximately 231 kilometers (144 miles) per pixel. Contrast has been enhanced to aid visibility of features in the atmosphere.
This image was taken using a filter sensitive to light near 727 nanometers, which is one of the near-infrared absorption bands of methane gas, one of the constituents of Saturn's atmosphere. Dark locales are generally areas of strong methane absorption, relatively free of high clouds. The bright areas are places with high, thick clouds which shield the methane below.
The clouded bands follow lines of constant latitude, and reflect the dominant effect of the planet's rotation on the dynamics of its atmosphere. Bands move at different speeds, and the irregularities at their edges may be due to either the differential motion between them or to disturbances originating below the visible cloud layer. Such disturbances might be powered by the planet's internal heat: Saturn radiates more energy than it receives from the Sun.
The dark spot at the south pole is remarkable because it is so small and well-centered. The spot could be affected by Saturn's magnetic field, which is nearly aligned with the planet's rotation axis, unlike the magnetic fields of Jupiter and Earth. From south to north, other notable features are the two white spots at roughly the same longitude but different latitudes, and the large dark oblong-shaped feature that extends into the bright equatorial band. The darker band beneath the bright equatorial region has begun to show a lacy pattern of lighter-colored, high altitude clouds, indicative of turbulent atmospheric conditions.
The moon Mimas (396 kilometers, 246 miles across) is visible to the left of the south pole. Saturn currently has 31 known moons, and Cassini scientists hope to discover new ones, perhaps embedded within the planet's magnificent rings.
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.