The Glow on the Moon's Horizon
The Moon has almost no air, so its sunsets should be instant and sharp. Cameras on the surface caught a glow along the horizon anyway.
What was reported
After the Sun set at their landing sites in 1967 and 1968, the cameras on NASA's Surveyor 5, 6 and 7 landers photographed a faint band of light along the western horizon. On Earth that would just be twilight, but the Moon has no real atmosphere to scatter the light.
In 1972, Eugene Cernan of Apollo 17 sketched what he saw from orbit just before lunar sunrise: streamers and bands of light rising above the horizon, like the rays of a sunrise on Earth seen through haze.
Explanations offered
The leading idea is that sunlight was scattered by fine dust lifted off the surface, perhaps by electric charges where daylight meets shadow. NASA's LADEE orbiter went looking for that dust in 2013 and 2014 and found far less than expected, so what lit the horizon is still debated.
- When
- 1967–1972
- Where
- Near Tycho crater, the Moon
- Witnesses
- The Surveyor landers' cameras, and the crew of Apollo 17
- Status
- Partly explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.