"There was a time when the solar system was much more interesting than it is today-when swordsmen dueled along the banks of the Grand Canal beneath the hurtling moons of Mars; when strange creatures writhed in the shadows of the mighty jungles of Venus; when Mercury's Twilight Belt marked a thin band of habitable territory between the lethal heat of the sunward side and the eternal cold of the side that faced the stars; when the many moons of the...