Astronomy Picture of the Day . ... The Apollo 15 mission to Earth's Moon was dedicated to better understanding the surface of the moon by exploring mountains, valleys, maria, and highlands. ... Two Worlds, One Sun, is the legend emblazoned on the Spirit rover's camera calibration target. ... Recorded by the rover's panoramic camera, the picture is part of Spirit's first color image of Mars - the highest resolution picture yet taken on the surface of another planet. ... Deimos: A Small Martian Moon . ...