They have new pictures of the disk on the Opportunity probe which just landed saturday. No hints yet, but let's have a look.
http://marsrovers.jpl.nasa.gov/gallery/all/1/p/002/1P128365104EFF0100P2205L4M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/1/p/002/1P128365137EFF0100P2205L1M1.JPG
Not exactly the highest quality images, but from the looks of it, it IS a different type of code, although it looks reminiscent of binary yet again... or perhaps braille..(sp)
[edit: addendum]
ll-ll--ll-llll-l-l!!!
