Rhea

[mmcirvin]

Rhea in as close to true color as I can make it:


Rhea in fake color (IR3/GRN/UV3):



As you can see, like most of the icy moons, Rhea is not very colorful. It looks a lot like Dione, except that the stain on the wispy trailing hemisphere is more subtly colored even in the compressed-spectrum pictures, and if the wisps are made of tectonic fractures like Dione's, we're still too far away to see (Rhea is quite a bit bigger than Dione).

I don't know whether that odd-looking straight line in the lower left is real or not. It shows up in all the frames, but I haven't tried correlating it with pictures taken from other angles. Update: It's real. It's in this Voyager 1 picture from 1980. I think it's probably a crater ray. What makes it look so weird in the Cassini image is that it coincidentally happens to be curved just such that, from Cassini's perspective, it doesn't look like it's following the curve of the surface.

Cassini got some pretty impressive, frame-filling pictures of Rhea from closer in. But they were of the side that is just craters and doesn't have any color features to speak of, so I haven't bothered trying to colorize them (though there are some that seem to have some bright rays or wisps near the horizon). It might be interesting to put together a big mosaic or two, but somebody will probably beat me to it.

Comments

[ronebofh.livejournal.com]

My wish is to get one of those Quicktime VR thingies that would let me rotate all of the moon in one go and back again if i want.

[mmcirvin.livejournal.com]

Steve Albers (http://laps.fsl.noaa.gov/albers/sos/sos.html) is doing a pretty good job of producing Cassini- and Voyager-based photomosaics that can be used as texture maps. The color matching isn't always perfect, but it's impressive given how quickly he incorporates new information. I've been using them in Celestia (http://sourceforge.net/projects/celestia/) to look at the landscapes from different angles and simulate Cassini and Huygens encounters.

Note, though, that these maps use a different longitude offset convention from Celestia, so to use them properly there you have to tweak them to put the prime meridian in the middle rather than at the edge.