The Composition and Geologic Setting of Lunar Far Side Maria

The dichotomy in the distribution of maria between the Earth facing side and the far side of the Moon has evoked many questions concerning the emplacement mechanisms, compositional variation, and source regions of lunar basalts. The near side maria have been well analyzed using a variety of Earth based, and lunar surface and satellite information. The Clementine mission has provided the first global mineralogical and chemical maps for the Moon. These data will allow us to gain knowledge of many lunar far side basalt deposits for the first time. Although the far side maria represents only about 1% of the surface of the Moon, these deposits provide insight into the crustal evolution, thermal history, and the interior of the Moon. Information on the composition, age, and volume of mare deposits will further our understanding of these questions. We are now studying several data sets, including multi-spectral images, crater statistics, and altimetry, to reconstruct and understand lunar volcanic evolution. Ultraviolet/visible (UVVIS) image data provide information of the composition of mare deposits. Ratios 415/750 provide information of titanium content and the 950/750 absorptions is correlated with the concentration of Fe2+ and mafic minerals. Crater statistics provide relative age determination, which can be used to estimate absolute ages. Knowing the range in ages of all the mare units on the far side will allow us to determine the duration of magmatism on the far side. Digital elevation maps from the Clementine altimetry allow us to estimate the deviation of mare units relative to the mean lunar radius to test if a systematic correlation in height of lava eruption surfaces and age might reflect a corresponding increase in depth of the zones of magma generation with time. Preliminary calibrations and multi-spectral mosaics have been generated for mare deposits within Antoniadi, Campbell, Compton and for Mare Moscoviense.