Mare Moscoviense a Window into the Interior of the Moon

Introduction: Mare Moscoviense is an enigma in many ways. Located within some of the thickest crust (80 km [1]) and at ~4 km above the mean lunar radius [2], these basalts were able to overcome buoyancy forces that have been proposed to impede the eruption of farside basalts [3]. In contrast, South Pole-Aitken basin exists in an area of the thinnest crust and 4-6 km below the mean lunar radius; thus, it should by all accounts be flooded and overflowing with basalt, yet the area of basalt in Mare Moscoviense, 35,000 km, is larger than any individual deposit within South PoleAitken. In addition, volcanism in Moscoviense occurred over a protracted period of time (potentially from Nectarian to upper Imbrian), in at least three different volcanic eruptive events. Compositionally, soils derived from these different flows exhibit a wide variation in titanium compositions, from low-Ti, ~1 wt.%, to high-Ti, 6-8 wt%. A similar range in TiO2 compositions is reported for basalt ponds within the Australe and South Pole-Aitken basins. We also report for this first time the presence of high-Mg orthopyroxene (opx) bearing basalt within Moscoviense. Together these data points suggest that the far side maria represent a compositionally heterogeneous mantle, able to partially melt over a prolong period of time, and that the rise of magma through the farside crust was minimally suppressed. Data: Clementine collected 11-band multispectral data (415, 750, 900, 950, 1000, 1100, 1250, 1500, 2000, 2620, and 2792 nm) at 100-200 meter per pixel spatial resolution for most of the lunar surface [4]. The Clementine data presented here are from the digital image model processed by the USGS with calibrations of [5-7]. From these data color ratio, FeO and TiO2 composition maps, and optical maturity index maps were yielded. Calculations of optical maturity (OMAT) are used to target optically immature craters that exhibit the best spectral contrast and signal-to-noise. Observations: Five different volcanic units are identified on the basis of their spectral properties and composition: high-Ti basalts, low-Ti basalts, ancient mare unit that exhibits the presence of high-Mg opx, cryptomare, and pyroclastic materials. The youngest unit in the basin is the high-Ti unit. The surface of this deposit exhibits 5-8 wt% TiO2 and 17-20 wt.% FeO (Fig 1.). Individual fresh craters, which represent compositions less contaminated by impact mixing by highland materials show higher FeO (20-21 wt.%) and TiO2 (8-10 wt%) contents (mare basalts within the Apollo basin and Australe basin exhibit similar TiO2 compositions but are less areally extensive).