Saturn, Spot On

As Cassini closes in on Saturn, its view is growing sharper with time and now reveals new atmospheric features in the planet’s southern hemisphere.

Saturn moon, Enceladus (499 kilometers, 310 miles across) at far lower right, from Ciclops Imaging Team. Saturn atmospheric phenomenon shown in southern hemisphere as dark spots between circulatory lines. The banner image shows the moon Dione (1,118 kilometers, 695 miles across) at far left, and the faint shadow of Mimas (398 kilometers, 247 miles across) closer to the rings. Credit: NASA/JPL/Space Science Institute

The spacecraft’s narrow angle camera took several exposures on March 8, 2004 which have been combined to create this natural color image. The image contrast and colors have been slightly enhanced to aid visibility. The spacecraft was then 56.4 million kilometers (35 million miles) from Saturn, or slightly more than one-third of the distance from Earth to the Sun. The image scale is approximately 338 kilometers (210 miles) per pixel. The planet is 23 percent larger in this image than it appeared in the preceding color image, taken four weeks earlier.

Atmospheric features such as two small, faint dark spots, visible in the planet’s southern hemisphere, will become clearer in the coming months. The spots are located at 38 degrees South latitude. Saturn’s equatorial region seems disturbed in the same way that it has been for the past decade, as revealed by observations from the Hubble Space Telescope. Researchers have speculated that the bright cloud patterns there are associated with water-moist convection arising from a deeper atmospheric level where water condenses on Saturn, and rising to levels at or above the visible cloud tops. Close analysis of future images by scientists on the Cassini-Huygens mission should help determine if this is the case.

Moons visible in these images: Mimas (398 kilometers, 247 miles across) at center in the banner, just next to the rings; Dione (1,118 kilometers, 695 miles across) at left, further from the rings than Mimas; and Enceladus (499 kilometers, 310 miles across) at image far right inset. The moons have had their brightness enhanced to aid visibility.

On May 18, Cassini officially enters the Saturn planetary system. On that day, the gravitational pull of Saturn begins to overtake the influence of the Sun and the probe crosses the outer limits of the most distant group of Saturnian moons, only weakly bound to Saturn and located tens of millions of kilometers from the planet.

The seven year voyage will end when Cassini’s main engine is fired, the spacecraft is slowed, and the probe enters Saturn orbit on July 1, 2004.

The Cassini-Huygens mission is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Office of Space Science, Washington, D.C.