CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Over the Limb
[For trouble viewing the images/movies on this page, go here]
Cassini acquired this view of Enceladus just after the spacecraft passed within 25 km (15 miles) of the surface on October 9, 2008. Remarkably, only a handful of craters are visible in this view, indicating the relatively young age of this surface.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 9, 2008 at a distance of approximately 38,000 kilometers (24,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 73 degrees. Image scale is 228 meters (746 feet) per pixel.

The Cassini Equinox Mission is a joint United States and European endeavor. 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 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.

For more information about the Cassini Equinox Mission visit http://ciclops.org, http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

Credit: NASA/JPL/Space Science Institute
Released: November 18, 2008 (PIA 10515)
Image/Caption Information
  Over the Limb
PIA 10515

Avg Rating: 9.30/10

Full Size 1020x1020:
JPEG 537 KB
PNG 474 KB
TIFF 1.0 MB


Alliance Member Comments
Red_dragon (Nov 25, 2008 at 4:19 AM):
One of the very best Enceladus images ever released.

Besides the rugged terrain, what amazes me of that moon is the lack (or nearly so) of largue -say on the order of 25-50 kilometers- craters. Put together with the ridges, and we'll possibly get Enceladus' crust is relatively thin; I'm even sure that in the past some part of Enceladus' surface has been liquid. So many to wonder for a world so small; imagine (as well as other worlds such as Io or Titan) how would have enjoyed this stuff planetologists of the pre-space age era as G. Kuiper.
Check out the CHARM presentation about Enceladus (PDF file!) at:

http://saturn.jpl.nasa.gov/multimedia/products/CHARM.cfm It's really worth.
Mercury_3488 (Nov 23, 2008 at 3:19 PM):
Hi Dragon_of_Luck_Mah_Jonng1971.

Thank you for your observations. Yes the similarities in the form of the ridges between Enceladus & Europa are striking.

But let's not forget. Europa is approximately 500 times the mass of Enceladus & the situation both are in are very different. We have seen activity at Enceladus but none as yet on Europa, the role of liquid water is suspect to say the least, as liquid water under the surface has not been conformed, just theoretical.

It certainly looks like cryolava has oozzed at first glance, but so far no cryovolcanic flows have actually been seen on either.

Even other suspect objects having shown considerable activity like Dione, Ariel & Titania, everything seen can be explained by tectonism, rather than eruptions.

I think these are cryovolcanic constructs myself, but so far the images are not conclusive.

Sippur Sulcus on Ganymede does look like as though cryolavas have flowed.

What would be interesting, would be to map the orientation of the fractures & compare the fractures here with the ones on Europa & also the rupes on Mercury, to see if the patterns are alike or very different.

Andrew Brown.
Dragon_of_Luck_Mah_Jonng1971 (Nov 18, 2008 at 5:39 PM):
Of course I'm meaning the long ridges visible in this image in my latest comment. Not the Halloween flyby's smaller passive ones ( without icy 'vulcanism' ) formed by compression ( I suppose ) at the south polar 'sulci' ; that are visible in the already famous 'Skeet Shoot' Images of this flyby.

I estimated that the ones of the image 'Over the Limb' are roughly half a mile ( 600 to 1000 m ) high.
Dragon_of_Luck_Mah_Jonng1971 (Nov 18, 2008 at 5:17 PM):
Just in this image of Enceladus there are many features of its surface activities. This image is breathtaking and mesmerizing ! It's showing again that the history of Enc's active regions is a very complex one. I calculated/estimated the large canyon at the right being approx. 6 to 7 km wide and approx. 1.5 to 2.5 km deep at its widest point visible here.
Above it there is an area of very complicated interesting features being mostly long cracks, terrains broken into 'plates' and ridges some of them being sinuous. There are also four ridges with strange neatly connections. These ones are running almost linearly and touching themselves by rather right angles ! That is strange - They're geologic features, no buildings by aliens, but they would be too neat for a usual Saturnian moon. But Enc is an unusual one ! ( The same ones are also on an older Enc mosaic by the Cassini Team. )
Some of the ridges in this image have got grabens on their tops but less neatly and less continuedly than the ones on Galileo's Europa Hi-Res images. ( Again ) I'm seeing similarities between Enc, Europa and Ganymed. Those grabens are confirming my older suspection I believe: The ridges on Europa and on Enc are being created by material of the upper mantle oozing through ( often linear ) cracks in the crust. Then creating a linear, icy feature. That is a kind of linear, icy 'vulcanism' not related to a spot like ( very often ) on Earth, Mars and Venus. I believe that on Europa and Enceladus there are also shapes of transition between ridges and rift zones e. g. an Europan ridge with a graben on top.
To create these Enceladan ridges there is needed I think a powerful geologic mechanism, a very active upper mantle and a crust which is not too rigid.
The active features on Enceladus, Europa and Ganymed are ( somewhat ) like rift valleys.
It's amazing that on Earth the mid oceanic rift zones ( sea floor-spreading ) also are owning a graben on their tops.

On Europa, Enceladus and ( a bit less ) on Ganymed it's also striking that newer linear features often have removed the older ones, especially on Enc.

I was very happy unexpectedly getting still a Hi-Res Enc image after the Halloween close flyby because no other close Enc flybys for roughly a year.

Want to add a comment?   Login (for Alliance Members) ... or ... Join the CICLOPS Alliance!