Signs of life

AP Photo/University of Colorado at Boulder - This photo released by University of Colorado at Boulder shows scientist Jeffrey Walker pointing to a green band within a chunk of sandstone-like rock he found in 2003, in the Norris Geyser Basin in Yellowstone National Park, Wyoming. An analysis determined that a green band was caused by a new species of photosynthetic microbes in the cyanidium group. NASA's Phoenix lander is looking for conditions near Mars' north pole that could support primitive life similar to extreme life on Earth.