Is there another Mars out there?
Within the next decade, NASA plans to develop space telescopes with super-sharp vision that can detect planets like Mars or Earth around other stars. In the meantime, learning as much as we can about our terrestrial next-door neighbors will help us understand what to look for, according to scientists at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
This image shows the Spirit rover probing its first target rock on Mars, Adirondack. Each mission to the red planet teaches us more about our terrestrial neighbor.
More than 100 planets have been discovered outside our Solar System, but they all are gaseous giants like Jupiter and Saturn. NASA's search for life beyond our Solar System hinges on finding smaller, rocky planets. As far as we know, only this type of planet could harbor liquid water on the surface, a feature considered essential to life.
Read more: http://www1.nasa.gov/missions/science/f_marsclues.html