Data from the Visual and Infrared Mapping Spectrometer (VIMS) on Cassini during its flyby
of the Moon in 1999 show a broad absorption at 3 micrometers due to adsorbed water and
near 2.8 micrometers attributed to hydroxyl in the sunlit surface on the Moon. The amounts of
water indicated in the spectra depend on the type of mixing and the grain sizes in the rocks
and soils but could be 10 to 1000 parts per million and locally higher. Water in the polar
regions may be water that has migrated to the colder environments there. Trace hydroxyl is …

Cassini flew by the Moon on August 19, 1999, and the Visual and Infrared Mapping
Spectrometer (VIMS) obtained 13 image cubes with a spatial resolution of about 175 km per
pixel with spectral coverage over the 3-? m region. The thermal emission from the lunar
surface is a low-frequency shape added to the spectra that complicates but does not prevent
the search for narrower water and hydroxyl absorptions. Thermal emission is lower in the
lunar polar regions due to the lower temperatures, reducing the complications. The thermal …