This image provided by NASA's Hubble Space Telescope shows a close-up of the red planet Mars when it was closest to the Hubble Space Telescope - just 55 million miles (88 million kilometers) away taken with Hubble's Wide Field and Planetary Camera 2. Mars was closest to Earth on Dec. 18, at 11:45 p.m. Universal Time (6:45 p.m. EST). Mars and Earth have a "close encounter" about every 26 months. These periodic encounters are due to the differences in the two planets' orbits. The planet appears free of any dust storms during this closest approach, however, there are significant clouds visible in both the northern and southern polar cap regions. (AP Photo/NASA)