DPS News and Notes
There were a number of results from the instrument teams from onboard Cassini. Many of the major results announced today were related to the rings and Saturn, and rightly so since admittedly they have gotten very little press coverage compared to the satellites so it is good they have their day in the sun. But this is a blog about the satellites, so who cares about those results ;-) Most of the Enceladus results were announced earlier at a press conference but some instrument teams did clarify them. VIMS last week announced they had found crystalline ice (absorption band at 1.65 microns) and simple organics (absorption band at 3.44 microns). During his talk, Bob Brown mentioned that the aborption band is attributed to a C-H stretch. In other words, it is some kind of organic compound, but VIMS can't tell what it is with just this one absorption band. Brown also announced that VIMS had not found any ammonia on Enceladus, shutting the door on ammonia-water volcanism. I'm not sure I agree with him there, but we may want to look at models that don't include ammonia. This also fails to explain how INMS saw N2. The CIRS principal investigator, Mike Flasar reported on results from Enceladus. In addition to the hotspot in the south polar region, CIRS found a relatively low thermal inertia, indicating that Enceladus is covered in unconsolidated material. Perhaps due to infalling E-ring material.
Finally, the RADAR team presented their results from T3. The most interesting features in that swath were the numerous linear to sublinear dark streaks, nicknamed cat scratches. These features have been interpreted as linear or longitudinal dunes, similar to those found in Saudi Arabia and Australia (near "Lake" Eyre). However, the RADAR team has been comparing the scratches to icy dunes in Antartica, which are visible in RADAR images of the continent, but not so much from the ground. The dunes take the form of changes in grain size rather than topographic features that one could see from the ground. Such an interpretation would jive with ISS' inability to resolve the scratches if both the dunes and the material that fills in between them are dark at 938 nanometers.
RADAR also released an image yesterday showing these dunes and a couple of drainage channels west of the "Circus Maximus" impact basin.