PIA06174: Race of the Moons

Race of the Moons

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This movie, showing six of Saturn’s small ring-region moons as they raced around the planet, was made from images taken by the Cassini spacecraft on Nov. 15, 2004.

The moons appear in following order (their diameters are given in parentheses): Janus (181 kilometers, or 113 miles), Atlas (32 kilometers, or 20 miles), Epimetheus (116 kilometers, or 72 miles), Prometheus (102 kilometers, or 63 miles), Pandora (84 kilometers, or 52 miles) and Pan (20 kilometers, or 12 miles). Each moon is marked by a colored circle that corresponds to the key at lower left.

While little detail on the moons is visible, it is possible to discern the irregular shapes of the larger ones seen in this movie. The rings are overexposed due to the long exposure times used (2 seconds per image): doing so makes the smaller, fainter moons (especially Pan) easier to detect. The direction of the moons’ motion is prograde, or clockwise as seen from Cassini’s vantage point beneath the ring plane.

In addition to the moons, knots in the F ring are visible here, as are several faint ringlets on both sides of that ring’s bright core. Faint knots also appear sporadically within the narrow Encke gap, where tiny Pan resides.

The movie consists of 73 images and spans a period of just over 14.5 hours, about an orbital period of the particles in the F ring.

The individual frames were taken at 12 minute intervals in visible light with Cassini’s narrow angle camera. The spacecraft was about 4.5 million kilometers (2.8 million miles) from Saturn when the images were taken. Image scale is approximately 26.5 kilometers (16.5 miles) per pixel.

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 mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit saturn.jpl.nasa.gov. For images visit the Cassini imaging team home page ciclops.org.

Image Credit: NASA/JPL/Space Science Institute

Source: NASA’s Planetary Photojournal: Image No. PIA06174