Oppy is the affectionate nickname of one of NASA’s twin Mars Rovers, Spirit and Opportunity. The sisters traveled to Mars in 2003 and explored the surface sending measurements and photographs back to Earth. This is the story of all they learned. The robot rover sisters were determined, patient, and persistent! Their mission was only meant to last 90 days, but they explored the planet for over 15 years. They shared all they learned with scientists on Earth, right up until the very last day of their mission.