The Mars Exploration Rovers Spirit and Opportunity were sent to Mars in 2004 to determine if life ever existed there, describe the Martian climate and geology, and prepare for future human exploration. Spirit landed in Gusev Crater and Opportunity landed in Meridiani Planum, sites thought to have once held water. Both rovers far exceeded their planned 90-day missions, with Spirit operating for over 1,000 days and Opportunity still active after over 1,000 days. The rovers used instruments such as cameras and spectrometers to analyze rocks and soil, finding evidence that water once shaped the landscape. Although the missions faced challenges like dust storms, the exploration of Mars continues to this day and has provided insights into the planet

1. Mars Exploration Rover: Spirit & Opportunity By Ray Ludwig