[X] My Assistant

[ugordan]

To wrap up the year, Cassini took a few Tethys low phase images from about 400 000 km.
A stretched color (IR/G/UV) composite:

[edstrick]

Rhea, Dione and Tethys all have darkened trailing hemispheres, with the darkening peaking approximately at the center of the trailing hemisphere (270 deg longitude???). This is opposite Iapetus's shading. In the post Voyager days, it was suspected to be some combination of magnetosphere modification of the more irradiated trailing surfaces and greater impact disturbance of the leading hemispheres. This still seems plausible at an "arm waving" level, I don't know the current state of theory.

[ugordan]

Here's an additional Tethys composite, showing roughly the same area as the first image. It's from the latest PDS release and is stretched color but was toned down to approximate natural color appearance. North is up on this one (the original image has north at left). Penelope is visible at center with I think Melanthius at 5 o'clock limb. The dichotomy is noticeable with the left hemisphere being slightly darker/orangish.