This past year President Bush announced a plan for space exploration that includes preparing for a human mission to Mars. Although the initiative is new, detailed plans for sending people to Mars have existed for decades. In the 1950's, Werner Von Braun outlined a comprehensive plan for Mars travel. At Apollo 11's launch in 1969, Vice President Spiro Agnew proposed Mars as the next goal for NASA. In 1989, President George H.W. Bush called for an extensive program of Moon and Mars explorations. And in the 1990's, author and engineer Robert Zubrin offered a simple and direct plan for Mars exploration. But reaching Mars within a reasonable time-frame will require more than plans; it will require vision: NASA must distinguish the problems that require new and imaginative research from those that can be solved using existing knowledge.