MISSION TO MARS by Michael Collins (Grove: $22.50; 288 pp.). Pity the poor space buffs like former astronaut Michael Collins, a self-confessed "dreamy-faced loon." While their eyes seek the stars, their ears must put up with Earth-bound pragmatists like former New York City Mayor Ed Koch, who has grumbled, "I just for the life of me can't see voting for monies to find out whether or not there is some microbe on Mars, when in fact I know there are rats in the Harlem apartments." Unable to exploit the old fears that once rallied support for the space program--of the tentacled Martians with salivating V-shaped mouths in "War of the Worlds," or of the slightly less menacing Communists in the Soviet Union--Collins tries appealing to survivalism (the planet's pink-and-orange landscape offers the best shot "if we are to establish ourselves as a multiplanet species"), the spirit of discovery ("Was Columbus' purchase of the Nina, Pinta and Santa Maria cost-effective?") and the need to inspire young scientists (the number of science and engineering doctorates, he claims, has been almost exactly proportional to NASA's appropriations). "Mission to Mars" is smart, spirited and sometimes even waggish, though Collins, who knows that major space missions are more important for their symbolism than their science, should have stopped waving the flag long enough to suggest a mission befitting our new, "borderless world": a joint venture backed by Europe, Japan and the U.S.