Your definition of "success" ?
= Failing to find the primary target of the mission?
There is NO liquid water on Mars, or under the surface anywhere we can reach.
Sure, there's some pretty geological bedding, and an internal layered structure to the ice caps, but we knew that already.
Still, every mission tells us new* things about any planet or moon...
* Sometimes it tells us the same thing, in a new way, or from a new angle.