Just about every two years, the planet Mars makes its closest approach to Earth... around 36 million miles. That's when we pack our robotic emissaries off to the Red Planet, timing their launches to spend the least effort to get there. Some fly around it... snapping pictures... Others land ... to sample its surface.... ...a few to crawl around its canyons and craters. These probes may pave the way for human explorers... and, perhaps permanent settlers... who'll dig deeper still... in search of answers to our most pressing question: Did Mars develop far enough -- and stay that way long enough -- for life to arise? And, if so, does anything live now within Mars' dusty plains... beneath its ice caps... or maybe somewhere underground? Mars does not give up its secrets easily ... it's almost as if the little planet is embarrassed. Over a century ago, a few observers thought they saw clues that Mars is alive. In 1877, the Italian astronomer Giovanni Schiaparelli noted markings... which he saw as a latticework of lines. He called them "canali" in Italian... meaning nothing more than "shallow channels" in English. American astronomer, Percival Lowell, found the lure of these features irresistible. He saw Schiaparelli's channels as artificial canals. He speculated that they carried melting snow from the poles to the dry interior. After all, on Earth, the Suez Canal had recently opened to ship traffic. The Panama Canal was beginning to be dug. The Martian canals, Lowell said, were <b>...</b>

Just about every two years, the planet Mars makes its closest approach to Earth... around 36 million miles. That's when we pack our robotic emissaries off to the Red Planet, timing their launches to spend the least effort to get there. Some fly around it... snapping pictures... Others land ... to sample its surface.... ...a few to crawl around its canyons and craters. These probes may pave the way for human explorers... and, perhaps permanent settlers... who'll dig deeper still... in search of answers to our most pressing question: Did Mars develop far enough -- and stay that way long enough -- for life to arise? And, if so, does anything live now within Mars' dusty plains... beneath its ice caps... or maybe somewhere underground? Mars does not give up its secrets easily ... it's almost as if the little planet is embarrassed. Over a century ago, a few observers thought they saw clues that Mars is alive. In 1877, the Italian astronomer Giovanni Schiaparelli noted markings... which he saw as a latticework of lines. He called them "canali" in Italian... meaning nothing more than "shallow channels" in English. American astronomer, Percival Lowell, found the lure of these features irresistible. He saw Schiaparelli's channels as artificial canals. He speculated that they carried melting snow from the poles to the dry interior. After all, on Earth, the Suez Canal had recently opened to ship traffic. The Panama Canal was beginning to be dug. The Martian canals, Lowell said, were <b>...</b>