What we initially conceived as a fairly simple geologic experiment on Mars ultimately turned into humanity's first real overland expedition across another planet. Spirit explored just as we would have, seeing a distant hill, climbing it, and showing us the vista from the summit. And she did it in a way that allowed everyone on Earth to be part of the adventure.
Steve SquyresWe have concluded that the rocks here were once soaked in liquid water. It changed their texture, and it changed their chemistry. We've been able to read the tell-tale clues the water left behind, giving us confidence in that conclusion.
Steve Squyres