The date was July 20, 1969, the day Apollo 11 landed the first human beings on the moon. It was the farthest we had ever traveled from the Earth and the first time humans ever stood on another object in our solar system and stared back in wonder at the world they called home. From there, it only seemed natural that humans would venture to Mars as well.
As early as 1946, the aforementioned German-American rocket scientist Dr. Wernher von Braun sketched out Marsprojekt, which called for no fewer than 70 astronauts aboard a fleet of 10 Mars-bound spacecraft [source: Wade]. As ambitious as this sounds, the project marked the first technically comprehensive design for a manned expedition to the red planet. It was far from the last, however, as both the United States and the Russian space programs continued to cook up manned Mars expedition studies throughout the rest of the 20th century. The Curiosity Rover, which landed on Mars in August 2012, has done some of the legwork for future explorations by collecting scientific samples and studying the planet's environment [source: NASA].
But sending a friendly rover to Mars is a lot easier than actually conquering the technical challenges of sending astronauts there, which include shielding them from radiation exposure and overcoming the health worries that long-term exposure to microgravity in space might cause. In 2010, President Barack Obama set a goal of launching a manned mission to Mars sometime in the 2030s, long after he leaves office. We'll see if that actually ever happens [source: Matson].