The 1-ton rover, Curiosity, has been exploring Mars since 2012, finding evidence of a large ancient freshwater lake in Gale Crater. My team developed and built a laser instrument, ChemCam, to analyze rocks and soils along the rover’s path. Imparting > 10 MegaWatts/mm2, pulses from the focused beam ablate material from the target, producing a luminous plasma that emits photons at wavelengths characteristic of the elements present in the target. The light is collected by a 4.5” diameter telescope on the rover’s mast and is spectrally analyzed. So far ChemCam has returned > 400,000 spectra from targets within 25 feet of the rover. The results show ancient Mars to be more Earth-like than ever expected. As the rover climbs higher in the crater, we have been able to trace a record of the drying out of Mars as its climate changed from wet and warm to cold and dry. At the end of the talk I will describe the new rover NASA is preparing for launch in 2020, including the next-generation ‘SuperCam’ instrument that we are building.