ORIENTALE BASIN AS A GUIDE FOR IDENTIFYING LUNAR BASIN DATEABLE IMPACT MELT AND ASSESSING IMPACT MELT DIFFERENTIATION (Invited Presentation)

Two fundamental questions face lunar scientists: 1) What is the absolute age of each lunar impact basin and thus the early impact flux curve?; and 2) To what degree did basin impact melt seas undergo differentiation? We compiled a 1:200,000-scale geological map of the lunar Orientale basin, focusing on identifying the most widespread and accessible occurrences of impact melt deposits from the basin-forming impact to help guide human and robotic sample-return missions to Orientale and other undated lunar basins. We assess the size and type of craters excavating through basin floor mare basalt cap rock that may be able to exhume, and provide access to, dateable basin impact melt, and we assess the possibility of impact melt sampling and melt differentiation for the large crater, Maunder. We also provide guidance for distinguishing impact melt produced by larger complex craters, such as Maunder, from excavated basins impact melt, and whether craters such as Maunder may have also sampled through the entire melt sea deposit. Our analysis finds six such sites that are predicted to have the same age--that of the Orientale-forming event--and provides guidance for assessing possible impact melt differentiation and distinguishing it from penetration through the entire melt sheet. Future landed missions could collect samples from these sites for in situ age dating and petrologic assessment and/or for return to Earth and subsequent age dating and analysis. By sampling and dating impact melt of known provenance from the Moon’s dozens of large basins, future work can anchor the chronostratigraphy of the Moon’s formative years. Such information could be then scaled to infer early Earth’s large impactor flux around the time of life’s first emergence.