Movie Clip
Click on the image for the movie
This video demonstrates two examples of the interpretation of tectonic
spreading along the "tiger stripe" fractures in the south polar terrain of
Saturn's moon Enceladus.
The first part of the video shows a simple example in which an old relict
tiger stripe is believed to have lost its tip after it was sheared off by
tectonic forces and pushed away from its parent by spreading. In the
meantime, the parent tiger stripe has managed to regenerate a replacement
tip, probably by the creation of new icy crust from upwelling soft ice.
The orphaned "clone" now sits by itself, connected to the parent only by
two parallel fault lines.
The movie shows that, if the orphaned tiger stripe tip can be slid along
the parallel faults back into place on the parent rift, the fit is
remarkably good. Striated material between the clone and the replacement
tip represents new icy crust material that must have been created during
the spreading process.
The second part of the video demonstrates how this video-reconstruction
technique can be used to infer a possible spreading history of the region
between two tiger stripes: Alexandria Sulcus and Cairo Sulcus. The process
begins by snipping-out and closing the gap that corresponds to Alexandria
Sulcus and its upraised flanks. The gap is closed by matching the
remaining right and left edges like a jigsaw puzzle. The closure is
accomplished by sliding along a prominent fault nearly perpendicular to
one end of Alexandria. This segment of the video is repeated four times
with arrows that mark previously offset features that come into alignment
after Alexandria is closed.
Next, Cairo Sulcus is closed along a lower fault that is parallel to the
one along which Alexandria was closed. After the Cairo is removed, the
closure is continued along the same fault until all of the intervening
terrain has been removed. During this process, a mysterious
14-kilometer-sized elliptical feature appears by matching a semi-circular
feature that previously existed on the right side of Cairo with the left
side of an oval-shaped feature that exists between Alexandria and Cairo.
In this way, the gap between Cairo and Alexandria can be closed
completely, but there remains a length of the fault that suggests even
more spreading may have occurred. Closing the gap all the way along this
fault results in the reappearance of a feature that resembles the
elliptical structure seen earlier. This feature is perhaps a relict impact
crater or the surface expression of a rising warm diapir or icy convection
cell.
This video was created based on images of the south pole of Enceladus
taken from this map, see PIA11126.
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.
