Saturn’s Ring Spokes are Back

Nope, that’s not an error in the photograph. The ghostly white stripe in Saturn’s rings was captured by Cassini on July 23, 2006. This is the first time that Cassini has seen spokes in Saturn’s rings in nearly a year, and the first time from the sunlit side of the rings. Some scientists think the spokes might be caused by meteoroid impacts onto the rings. Others suggest they’re created by an instability in Saturn’s magnetic field.

This image from the Cassini spacecraft shows a ghostly white streak, called a spoke, in Saturn’s B ring. This is the first sighting of a spoke in nearly a year, and the first spoke seen by Cassini on the sunlit side of the rings.

It is also the first spoke seen at high phase angle — that is, the angle formed between the sun, the rings and Cassini. In this geometry, the feature appears white (instead of black) against the rings because the very small particles comprising the spoke preferentially scatter light in the forward direction (i.e. toward Cassini), making the spoke brighter than the background rings.

The clear-filter image was taken in visible light with the Cassini spacecraft wide-angle camera on July 23, 2006, at a distance of approximately 692,000 kilometers (430,000 miles) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 115 degrees. Image scale on the sky at the distance of Saturn is 38 kilometers (23 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 operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release