NASA Sets Its Sites on Mars Sky & Telescope

After an exhaustive two-year selection process, NASA has announced the target zones on Mars where a pair of sophisticated rovers are to land early next year. The first of these Mars Exploration Rovers (MER A) will head for a large, sediment-filled crater called Gusev, while MER B is going to the mysterious flatlands of Meridiani Planum. Both sites show ample evidence, though in different ways, that liquid water was present in ancient times.