A fine spray of small, icy particles emanating from the warm,
geologically unique province surrounding the south pole of
Saturnís moon Enceladus was observed in a Cassini
narrow-angle camera image of the crescent moon taken
on Jan. 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 measured by other Cassini instruments
(reported in September, 2005) at altitudes as high as 400
kilometers (250 miles) above the surface.
Imaging scientists, as reported in the journal Science on March
10, 2006, believe that the jets are geysers erupting from pressurized
subsurface reservoirs of liquid water above 273 degrees Kelvin (0
The image at the 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 the 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 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.
This caption was updated on March 9, 2006.
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