The principle cause of our intense interest in Mars in the decades before the dawn of the space age was that Answers: A. a few astronomers believed that they saw evidence of an intelligent civilization on Mars. B. Mars has seasons just like the Earth and therefore should be inhabitable by humans. C. Mars has an unusual surface color and global dust storms, creating strange weather patterns. D. Mars has unusual orbital properties making our understanding of its motion around the Sun very difficult.

The principle cause of our intense interest in Mars in the decades before the dawn of the space age was that Answers: A. a few astronomers believed that they saw evidence of an intelligent civilization on Mars. B. Mars has seasons just like the Earth and therefore should be inhabitable by humans. C. Mars has an unusual surface color and global dust storms, creating strange weather patterns. D. Mars has unusual orbital properties making our understanding of its motion around the Sun very difficult.