[X] My Assistant

[Guest_AlexBlackwell_*]

The June 1, 2006, issue of Nature has a new paper by Nimmo and Pappalardo entitled "Diapir-induced reorientation of Saturn's moon Enceladus" as well as an accompanying News and Views piece by Paul Hanlon. For the specific links, see the Editor's Summary.

[Guest_BruceMoomaw_*]

Pappalardo and Nimmo's LPSC abstract on the idea is at http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2113.pdf , and a related one on the apparent compression/extension stress patterns in Enceladus' crust around the area (which may well be important evidence supporting the theory) is at http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2182.pdf . I don't, however, quite know whether or not this theory meshes easily with Porco's observation that the center of thermal activity has been slowly migrating southward across Enceladus' ice surface over the eons. Comments, Bob?

[volcanopele]

I don't, however, quite know whether or not this theory meshes easily with Porco's observation that the center of thermal activity has been slowly migrating southward across Enceladus' ice surface over the eons. Comments, Bob?

I have reread the relevant sections of our paper and I don't see any reference to the idea that the thermal activity has been migrating southwards. I think Squyres et al. 1983 might, in the Voyager 2 observations of cratered terrain in the northern and sub-Saturnian hemispheres, in that craters counts get progressively lower as you go south...in the sub-saturnian cratered terrains. I don't see where this is implied or discussed in Porco et al. 2006. From the looks of it, we mention three sites of thermal activity in the past: the trailing hemisphere as seen in Sarandib and Diyar Planitiae, the leading hemisphere (55 South-45 North; 45-130 West), and the south polar terrain.

You may be refering to a table in Porco et al. 2006 showing craterings statistics and calculated surface ages for 4 geologic units and the ultra high-res WAC. I should note that the latitude range for Unit III (Samarkand Sulci) is mislabeled (I think that should read 55-65 North, or there abouts), it shouldn't say south, or at least not that far south.