"The planet Mars," writes Robert Zubrin, "is a world of breathtaking scenery, with spectacular mountains three times as tall as Mount Everest, canyons three times as deep and five times as long as the Grand Canyon, vast ice fields, and thousands of kilometers of mysterious dry riverbeds. Its unexplored surface may hold unimagined riches and resources for future humanity, as well as answers to some of the deepest philosophical questions that thinking men and women have pondered for millennia. . . .

But all that Mars holds will forever remain beyond our grasp unless and until men and women walk its rugged landscapes."34

In one paragraph, Zubrin explains why human exploration of Mars is such an important aspect of any future space exploration. Only humans have the ability to see, feel, and touch the red planet, ponder their surroundings, and draw conclusions based on their...