Curiosity Rover Discovers Book-Shaped Rock Carved by Water on Mars.

NASA's Curiosity rover has discovered a book-shaped rock on Mars, which is believed to have been carved by water trickling in the area billions of years ago when the planet was much wetter. The harder materials of the rock were left behind after softer rock was sand-blasted away by the wind. Curiosity has been exploring Mars' Gale Crater since August 2012 and has made key discoveries, including the potential evidence of ancient life through organics and the discovery of persistent liquid water on ancient Mars.