The Earth.
Source: http://www.nasa.gov/images/content/115334main_image_feature_329_ys_full.jpg Alt: http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001138.html (direct link). http://en.wiktionary.org/wiki/File:The_Earth_seen_from_Apollo_17.jpg
Author: NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans