Spirit and its twin rover, Opportunity, both landed on the Red Planet in 2004. Spirit's location was Gusev Crater, where it operated for six years beaming back information to Earth. In 2010, however, Spirit got stuck in a sand trap and was unable to move; in the fading winter sunlight, it ceased communications with Earth. Among Spirit's major discoveries was finding hematite on Mars (which is formed in water). When it was stuck on Mars, it ended up making another discovery by accident. As its wheels were spinning in the soil, it revealed a very silica-rich layer that is similar to what is found on Earth when hot springs and volcanic rocks mix. It's an environment that on Earth, is rich in microbial life.
Image: A view of Gusev Crater, where the Spirit rover operated between 2004 and 2010. Credit: NASA/JPL/University of Arizona