Both a detailed literature survey and a new
observational study were performed to determine and
extend the knowledge of spectral reflectivity differences
(color differences) on the lunar surface in the extended
visible wavelength region. A survey of the extensive
and disorganized literature revealed few positively
known facts and indicated the need for an accurate, multi-passband observational study of a number of lunar areas
of differing morphology. A 21-filter (0.4µ- 0.8µ),
double beam photoelectric photometer was designed and
constructed to observe differentially 83 lunar areas,
some many times, to an accuracy of 0.1% to 0.3%. Some
results were the discovery of: (1) many color variations
up to 10% with some to about 60%, (2) a dependence of
relative color on phase angle but no temporally varying
luminescence, (3) broadband absorption features on
spectral reflectivity curves and possibly some less broad,
low amplitude (0.2%- 0.5%) humps, (4) a dependence of
spectral curve shape on lunar morphology and, (5) no
universal dependence of color on brightness, although
some mare areas show this tendency. These results indicate
that color differences are caused mainly by compositional differences and that the shapes of the spectral reflectivity curves give some indications of the rock and mineral composition of the lunar surface
