A fine spray of small, icy particles emanating from the warm, geologically unique province surrounding the south pole of Enceladus was observed in a Cassini narrow-angle camera image of the crescent moon taken on January 16, 2005.
Taken from a high phase angle of 148 degrees – a viewing geometry in which small particles become much easier to see – the plume of material becomes more apparent in images processed to enhance faint signals.
Imaging scientists have measured the light scattered by the plume's particles to determine their abundance and fall-off with height. Though the measurements of particle abundance are more certain within 100 kilometers (60 miles) of the surface, the values measured there are roughly consistent with the abundance of water ice particles made by other Cassini instruments (reported in September, 2005) at altitudes as high as 400 kilometers (250 miles) above the surface.
The image at left was taken in visible green light. A dark mask was applied to the moon’s bright limb in order to make the plume feature easier to see.
The image at right has been color-coded to make faint signals in the plume more apparent. Images of other satellites (such as Tethys and Mimas) taken in the last 10 months from similar lighting and viewing geometries, and with identical camera parameters as this one, were closely examined in order to demonstrate that the plume towering above Enceladus' south pole is real and not a camera artifact.
The images were acquired at a distance of about 209,400 kilometers (130,100 miles) from Enceladus. Image scale is about 1 kilometer (0.6 mile) 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 Cassini-Huygens mission for NASA's Science Mission Directorate, 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.