In the 1960's robotic landers observed a glow above the lunar horizon before sunset, that shlouldn't be there if the Moon has no atmosphere. Now computermodel suggest an explanation, that can be explained i 2012 when LADEE reaches the Moon

Timothy Stubbs from University of Baltimore says:
"Lunar horizon glow (LHG) was first observed between 1966 and 1968 by TV cameras aboard the Surveyor landers -- robotic precursors to the manned Apollo landings -- specifically Surveyor 5, 6 and 7, and possibly Surveyor 1"

The LHG has of course been mentioned in many of the Lunar-hoax theories than runs around on the Internet, but has a fairly simple explanation:

Whenever the Moon is hit by a meteor, dust, grains and a diversity of vapors are thrown out in space - but some or most of it, with speed below the lunar escape-vcelocity. This dust and gasses will slowly return to the surface of the Moon, creating a temporary dustcloud over the surface of the Moon

Stubbs says: "The high altitude observations are particularly controversial. If LHG is present at high altitudes, then the suggestions are that it is produced either by sunlight scattering from dust, or by resonant scattering of sunlight from neutral sodium atoms in the exosphere. However, if sodium is producing the LHG, it should be seen up to altitudes in excess of 1,000 km (about 620 miles), but the LHG observed so far only appears to extend about 100 km  above the horizon. Our predictions indicate that the LHG observations appear to be more consistent with the presence of exospheric dust."

"The scattering of sunlight by dust in the lunar atmosphere could mean that the moon is not as good a location for sensitive astronomical observations as has previously been assumed. This characteristic of the lunar environment needs to be well characterized before an informed judgment regarding the benefit of lunar-based telescopes can be made," says Stubbs

NASAs planned lunar orbiter LADEE will hopefully solve these questions, when it reaches the Moon in 2012-13. LADEE is currently under study for launch in 2012 on a Minotaur-V. LADEE is designed to characterize the tenuous lunar atmosphere and dust environment from orbit. The scientific objectives of the mission are:

1) Determine the global density, composition, and time variability of the fragile lunar atmosphere before it is perturbed by further human activity; and

2) Determine the size, charge, and spatial distribution of electrostatically transported dust grains and assess their likely effects on lunar exploration and lunar-based astronomy. further objectives are to determine if the Apollo astronaut sightings of diffuse emission at 10s of km above the surface were Na glow or dust and document the dust impactor environment (size-frequency) to help guide design engineering for the outpost and also future robotic missions.

The current launch readiness date is May 2012 with launch windows opening any time after that. The nominal science orbit will last 100 days. The orbiter will carry a neutral mass spectrometer, an ultraviolet/visible spectrometer, and a dust detector. The total science payload mass must be less than 20 kg with normal power of 60 W and a 100 W maximum. There is also a technology demonstration, the Lunar laser Communication Demonstration. Communications will be via S-band with a 10 Kbps science data rate. Total mass of the orbiter will be approximately 130 kg.

READ MORE on LADEE at  the LADEE homepage