J. J. Rennilson1 and D. R. Criswell2
(1)  Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, Calif., USA
(2)  The Lunar Science Institute, Houston, Tex., USA

Received: 13 August 1973 
Abstract  Each of the Surveyor 7, 6, and 5 spacecraft observed a line of light along its western lunar horizon following local sunset. It has been suggested that this horizon-glow (HG) is sunlight, which is forward-scattered by dust grains (~ 10µ in diam, ~ 50 grains cm–2) present in a tenuous cloud formed temporarily (lap 3 h duration) just above sharp sunlight/shadow boundaries in the terminator zone. Electrically charged grains could be levitated into the cloud by intense electrostatic fields (> 500 V cm–1) extending across the sunlight/shadow boundaries. Detailed analysis of the HG absolute luminance, temporal decay, and morphology confirm the cloud model. The levitation mechanism must eject 107 more particles per unit time into the cloud than could micro meteorites. Electrostatic transport is probably the dominant local transport mechanism of lunar surface fines.
This work was supported in part by the California Institute of Technology under Grant NGR 05-002-158, and in part by the Lunar Science Institute, which is operated by the Universities Space Research Association under Contract No. NSR-09-051-001 with the National Aeronautics and Space Administration. This paper is Lunar Science Institute Contribution No. 163.

Surveyor Observations of Lunar Horizon-Glow

From Richard Hoagland's work...

"This may be a photograph of the extraordinary glass dome covering the region of the moon known as Sinus Medii. It was taken by the unmanned Surveyor 6 on November 24, 1967, one hour after sunset."

NASA Photo ID: AS16-123-19657      File Name: 10075873.jpg
Film Type: 70mm BW                 Date Taken: 04/21/72
Title: Earth, photographed in far-ultraviolet light with the ultraviolet camera
Description:
The Earth, photographed in far-ultraviolet light (1304 Angstrom) by 
Astronaut John W. Young, Apollo 16 commander, with the ultraviolet camera. 
The auroral belts 13 degrees either side of the magnetic equator can be
seen  crossing each other on the middle of the right side of the Earth. 

Subject terms:
APOLLO 16 FLIGHT 
APOLLO PROJECT 
CAMERAS 
EARTH (PLANET) 
PHOTOGRAPHY 
ULTRAVIOLET PHOTOMETRY 

Surveyor 6

Surveyor 6 was the sixth lunar lander of the Surveyor program that explored the Moon.

    * Launched November 7, 1967; landed November 10, 1967
    * Weight on landing: 299.6 kg (660.5 lb)

Surveyor 6 landed on the Sinus Medii. A total of 30,027 images were transmitted to Earth.

This spacecraft was the fourth of the Surveyor series to successfully achieve a soft landing on the moon, obtain postlanding television pictures, determine the abundance of the chemical elements in the lunar soil, obtain touchdown dynamics data, obtain thermal and radar reflectivity data, and conduct a Vernier engine erosion experiment. Virtually identical to Surveyor 5, this spacecraft carried a television camera, a small bar magnet attached to one footpad, and an alpha-scattering instrument as well as the necessary engineering equipment. It landed on November 10, 1967, in Sinus Medii, 0.49 deg in latitude and 1.40 deg w longitude (selenographic coordinates) - the center of the moon's visible hemisphere. This spacecraft accomplished all planned objectives and also performed a successful 'hop' rising approximately 4 m and moving laterally about 2.5 m to a new location on the lunar surface. The successful completion of this mission satisfied the Surveyor program's obligation to the Apollo project. On November 24, 1967, the spacecraft was shut down for the 2 week lunar night. Contact was made on December 14, 1967, but no useful data were obtained.

Wikipedia - Surveyor 6

Sinus Medii, November 1967

Surveyor 6 touched down in Sinus Medii, at 0.49 N, 358.60 E. Once on the surface, the spacecraft took a series of pictures and soil samples. Then, on November 17, controllers ordered the spacecraft's engines to fire, lifting Surveyor 6 off the lunar surface 3 meters (10 feet) and setting it down again a few feet from the original landing site. The spacecraft then took pictures of the former landing site, checking for evidence of a crater created by the rocket's exhaust. No crater was found, indicating that the Moon's surface was solid enough to support a manned landing. This panorama was scanned from a photographic print of a hand-assembled mosaic, then digitally reconstructed and cleaned of visual defects by Philip Stooke.

Surveyor 6 

Surveyor 6 touched down in Sinus Medii. Once on the surface, the spacecraft took a series of pictures and soil samples. Then, on November 17, controllers ordered the spacecraft's engines to fire, lifting Surveyor 6 off the lunar surface 3 meters (10 feet) and setting it down again a few feet from the original landing site. The spacecraft then took pictures of the former landing site, checking for evidence of a crater created by the rocket's exhaust. No crater was found, indicating that the Moon's surface was solid. Last contact with the spacecraft was December 14, 1967. 

The Planetary Society: Missions to the Moon