Are we alone? It's a question humankind has asked for a long time. Of all the planets in the solar system, Mars shows the most promise of having nurtured life.
In order to know more about the Red Planet, NASA launched twin robot geologists Spirit and Opportunity on June 10 and July 7, 2003.
Spirit, which landed on Mars on January 4, 2004 sent back stunning images of the Red Planet.
NASA Mars Mission team members looking at the first images transmitted by Spirit. The photographs arrived at the Jet Propulsion Laboratory in California.
Photograph: Bill Ingalls/NASA via Getty Images