The moon is generally thought to be a dry place, and the discovery of water on its surface comes as an unexpected — and exciting — surprise for researchers. Carolina K. Smith/ hide caption

itoggle caption Carolina K. Smith/

This radar image taken by Cassini in July 2006 of Titan, one of Saturn's moons, provides convincing evidence that it is covered by large bodies of liquid. NASA/JPL/Space Science Institute hide caption

itoggle caption NASA/JPL/Space Science Institute

Both young infants and dogs sometimes ignore what they see with their own eyes and instead trust a human "teacher." Dogs may have evolved this trait to help them live with people. hide caption

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