A New High-Detail, Color Vision Deficiency-Friendly Geological Map of the Orientale Basin (Moon)

The Orientale Basin, centered at ~19°S, ~93°W, is one of the most characteristic features on the surface of the Moon. Constituted by three concentric rings, the largest of which is between 930 and 950 km in diameter, this multi-ring basin is one of the youngest large impact basins on the Moon (Orientale is estimated to date back ~3.81 Ga) and one of the best-preserved large basins in the entire Solar System. Inside, its central depression hosts a relatively thin infilling of dark, smooth material interpreted as a mare basalt, whilst outside the outermost ring an ejecta blanket drapes the surrounding topography sometimes reaching over 1,400 km from the center of the basin. Throughout the years, the importance of the Orientale Basin has led to the creation of several geological maps at various scales, none of which, however, a scale greater than 1:200,000. Additionally, these maps never try to put together the two main methodological approaches adopted internationally up to this point at global scale for the Moon. Our work tries to bridge this gap by presenting a new medium-to-large-scale (1:118,000) geological map of both the inner and outer facies which makes use of a combination between a traditional planetary geological scheme and a more morphometric criterion.

The map was created with the latest long-time stable release of QGIS (vrs. 3.40) mainly using the 59 m/px resolution Lunar Orbiter Laser Altimeter (LOLA)-Kaguya Shaded Relief and the 59 m/px resolution LOLA-Kaguya DEM. These two datasets, only covering latitudes within ±60° were utilized to distinguish the different units and subunits based off their general morphology, textures, and locations, but also to identify the structures. The 100 m/px resolution, grayscale mosaic of the Lunar Reconnaissance Orbiter Wide Angle Camera (LROC-WAC) and the 118 m/px LOLA elevation model were additionally used to make up for the missing portion of the LOLA-Kaguya datasets. The Clementine UVVIS colored mosaic (200 m/px) and the mineral abundance (wt% of Ol, Cpx, Opx, Pl, FeO) Kaguya mosaics also allowed to add a layer of information regarding differences in composition of apparently visually uniform features and terrains.

We managed to identify over 20 between units and sub-units that we grouped based on the terrain or morphological feature they are related to (e.g. crater, mare, …), and over 10 classes of structures. Our final product represents the highest resolution map available for the Orientale Basin and when compared with already existing medium-scale maps, appears to depict with more detail and accuracy its complexity. Additionally, we made use of a color vision deficiency-friendly color scheme to make the map more accessible also to that part of the population having limited sensitivity to colors.