Curiosity isn’t just on a scenic mission either, it’s got some real work to do while it’s traipsing around Mars. It has an X-ray diffraction and fluorescence instrument called a CheMin that identifies the minerals in the samples gathered by the robotic arm. It’s going to analyze the upper atmosphere, to try and figure out where Mars water supply went.
Which is really funny in a historical context. Giovanni Schiaparelli first suggested there were canals (and therefore water) on Mars in 1877, as a result of what we now know to be a optical illusion. By 1909 Martian Canals had been completely discredited and until the Mariner 9 mission in 1971 that was the end of the story.
Mariner 9 found surface features that suggested water had eroded the surface, canyons and river beds. But now, with Curiosity, we are not only answering the question of if Mars had water (not only did it, it might still have water!) but where that water went!
Finally – as Jon Stewart pointed out – Curiosity has a death ray! Well, an instrument named ChemCam that uses laser pulses to vaporize thin layers of material from Martian rocks or soil from twenty feet away! Kind of a death ray, if you’re a small piece of rock.