13.04

On the Highland Crust Diversity and Mare-Highland Transitions in the Mare Humorum Region of the Moon

P.D. Martin (PGD/HIGP/SOEST, Univ. of Hawaii), P.C. Pinet, S.D. Chevrel, Y.H. Daydou (UMR5562/CNRS/OMP, Toulouse, FRANCE)

We present a high spatial resolution (340m) analysis of the spectral and compositional properties of the lunar surface, focused on the Humorum basin region. The processing and calibration of more than 2000 raw Clementine frames has led to the production of an extended (600 kms x 450 kms) multispectral image-cube in the 0.40-1.0 micron wavelength range. The spatial information derived from a linear mixing modeling as well as from the information of maturity and titanium (mare units) and iron abundance, is discussed in relation with the previous interpretations of remotely-sensed data of the region. The following inferences are made in an attempt to characterize the nature and origin of the spectrally identified materials. The spectral properties of the most extended western highland unit exhibit a concentric distribution which is found associated with the ring structure of the basin. In particular, on the mare-bounding ring, we have established the presence of an extended pure anorthosite unit (Fe content <3%). Another highland area, low in topography and located northwest of Mersenius toward Herigonius and Letronne regions, has spectral characteristics indicating undefined deposit materials, with local mare-like contributions. Within the southwestern highlands (25 to 100 kms from the basin's boundary), the spectral features of the darkest terrains indicate mare optical properties, possibly related to the presence of cryptomare deposits. The study of mare-highland relations reveals the great complexity of the region, with variable mixing gradients suggesting different processes of physical mixing of materials throughout the geologic boundaries of the basin.