Jets of high-density gas detected by Cassini's Ultraviolet Imaging
Spectrograph on Saturn's moon Enceladus match the locations of dust jets
determined from Cassini images, labeled here with Roman numerals. The
spectrograph pinpointed the locations of individual gas streams in the
plume in a "stellar occultation," which involves measuring the light of a
star (in this case, zeta Orionis), as it passed behind the plume from
Cassini's viewpoint.
The blue line in this projection shows the path of the starlight through
the plume, over the south polar region of Enceladus. The instrument looked
at the star across this path in the direction indicated by the short blue
lines.
Some of the dust jets appear to merge together in stellar occultation
data. The dimming of starlight labeled "a" was caused by dust jets V and
VII. The dimming of starlight marked as feature "b" may be associated with
dust jet I if the jet is not perfectly vertical. Dimming of starlight
labeled "c" corresponds to dust jet VI, and "d" is dust jet III, with dust
jet II in between. The individual jets come from sources with an area of
less than 300 by 300 meters (1,000 feet square)—about the size of a football stadium—probably stretched out rectangularly along the tiger
stripes. The new data indicate that the water molecules are blasting off
from Enceladus at faster than 600 meters per second (about 1,200 miles per
hour).
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 was designed, developed and assembled at JPL. The
ultraviolet imaging spectrograph was designed and built at, and the team
is based at the University of Colorado, Boulder.
For more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov. The ultraviolet imaging spectrograph team home
page is at http://lasp.colorado.edu/cassini.
