Just when you thought you had seen every type of robotic platform something new comes along that is just so amazing that you can't help be impressed. The MorpHex is a an ongoing project but it has progressed quite a lot since we first saw it in "naked" form.
You can see that it is a very clever arrangement of servos and some motors operating an "iris" like mechanism. Personally I liked the way it looked before, but now it has an outer case in the form of a sphere.
It can transform from a closed sphere to a walking hexapod in no time at all.
If you plan to copy the design it is worth knowing that it uses 25 servos, a Basicmicro AR-32 controller and an XBee radio. This isn't going to be cheap. Also consider the problems of writing the code to make it transform and walk - it's an interesting challenge. There are also lots of questions to answer like how well could it get about by simply rolling? With a few changes to its outer cladding it could easily be a useful robot in many difficult situations.
The idea of using one as a planetary explorer seems entirely reasonable, but before you start to think that it's a NASA or big company project I should add that it is the work of one man in his part time. If you want more information about the build then visit Zenta Robotic Creations and admire the work of Kare Halvorsen.