This image shows the coronal and zodiacal light (CZL) on the moon as seen by the Clementine spacecraft. The white area is the CZL and the bright object in space is the planet Venus. The CZL glow of the moon was noticed by several astronauts. It is a lunar horizon glow that occurs when the moon is out of the sun's direct light. Since the moon has no atmosphere, experts aren't entirely sure why it happens. Further, it is not always seen. NASA hopes that the launch of the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft will clear up the mystery of the CZL glow.