http://www.zbrushcentral.com/zbc/showthread.php?t=074190
This is an article from one of the artists for this film. Note how he made the planet Mars.
I think he did it the hard way. It was effective, so there's no use saying, "Hey, over here! See what Terragen 2 can do!'
I just hope he tries out Terragen 2. Four or five computers rendering a thirty second sequence could render the anim in a couple days to a week.
It would probably be easiest to do the craters in a dedicated shader in Maya that makes crater noises but if there is no erosion filter then..... or just use World Machine that i think has a crater device and slightly erode it. Is there even a way to do many craters in Terragen 2 and erode them well?