In 1877, Italian astronomer Giovanni Schiaparelli announced that he had observed "canali" on the surface of Mars. Though "canali" was best translated as "channels," some people interpreted it to mean "canals," which implied artificial structures and thus evidence of intelligent life.

Though we now know there are no Martians, two spacecraft currently orbiting the Red Planet have provided evidence that there was once flowing water on Mars. The Global Surveyor spacecraft has photographed giant channels carved out of the plains of Mars by ancient floodwaters that probably poured out of volcanic issures. There aren't many craters in the channels, which suggests that they formed only in the last several million years, which is almost yesterday, geologically speaking, since Mars is about 4.5 billion years old.

Where's the water now? Some of it may have been lost to space, but the Mars Odyssey spacecraft recently found evidence of large amounts of ice just beneath the surface of the Martian South Pole. There may also be ice beneath the North Pole, where Odyssey will look in the coming months.