Look up from your BlackBerry one night. That is the moon. On it are exactly 12 sets of human footprints -- untouched, unchanged, abandoned. For the first time in history, the moon is not just a mystery and a muse, but a nightly rebuke. A vigorous young president once summoned us to this new frontier, calling the voyage "the most hazardous and dangerous and greatest adventure on which man has ever embarked."