NASA / JPL / SSI / color composite by Emily Lakdawalla
Janus against Saturn, March 27, 2012
Cassini captured this view of Janus floating in front of Saturn on March 27, 2012.
Around March 27, 2012, Cassini took lots of great photos of Saturn's moons. This one shows Janus, a moon about a third the diameter of Enceladus that orbits between the F and G rings. The background is yellow in this infrared-green-ultraviolet color composite because the moon is sitting in front of Saturn.
There is a surprising range of albedo variations across Janus and within its craters; in fact, it reminded Emily Lakdawalla of contemporaneous views from Dawn at Vesta. Janus is quite a bit smaller than Vesta, but it's made of weaker stuff (ice, rather than rock); Vesta-sized icy moons look much smoother. But Janus doesn't have as many craters as Vesta does.
It took quite a bit of work on the component images, which were taken from Cassini's raw images website (UV, green, IR), to erase the bright marks of energetic particles striking Cassini's camera detector; that work involved some paining on Janus, especially on its night side, and the use of the Photoshop dust and scratches filter on Saturn. Two frames were resized very slightly to compensate for Cassini's changing distance to Janus in the time separating the capture of the three frames.