NASA's ground crew maneuvered the Lunar Atmosphere and Dust Environment Explorer (LADEE) just two miles above the Apennine Mountains on the bright side of the moon this weekend to collect particles from the mysterious "horizon glow." Apollo 17 astronauts first spotted the lunar horizon glow just before sunrise during their 1972 mission, but it went unexplained.
Two weeks before LADEE's mission expires and ground controllers set an impact trajectory for the dark side of the moon (planned for April 21), NASA scientists sent LADEE to debunk the crystal smog–like glow.
LADEE's star tracker plays the role of Apollo astronaut this time, angled toward the moon's horizon to replicate what they saw—or what they think they saw. Here's their best guess: The sun's ultraviolet rays electrically charge lunar dust particles (LADEE says neon, magnesium, and aluminum), which mass into a cloud just above the moon's surface and catch the morning's first light.
The mission is somewhat of a shot in the dark with NASA scrap metal. "The moon's gravity field is so lumpy and the terrain is so highly variable with crater ridges and valleys that frequent maneuvers are required or the LADEE spacecraft will impact the moon's surface," LADEE project manager Butler Hine told NASA. "Even if we perform all maneuvers perfectly, there's still a chance LADEE could impact the moon sometime before April 21."