Former astronaut Neil Armstrong, whose 1969 moon landing transformed human exploration and made him the most famous aviator since Charles Lindbergh, spent the following decades shunning the limelight. But his death, at 82, confirmed Saturday, rekindled memories of that timeless achievement.

As commander of the Apollo 11 spacecraft and the first man to step on the lunar surface, Mr. Armstrong punctuated his exploit with the memorable phrase that it marked "one small step for man, one giant leap for mankind." The mission forever...