GEOLOGIC MAPPING OF THE ARISTARCHUS PLATEAU, MOON

Introduction: The Aristarchus Plateau is a unique region on the Moon, hosting its highest concentration of rilles including the widest and deepest rille, its most extensive dark mantle deposits, as well as rare exposures of both, very olivine-rich and very silicate-rich materials. The plateau has been considered as one of the most promising exploration sites apart from the lunar poles for decades. As there exists no dedicated, peer-reviewed map of the Aristarchus Plateau, we are producing a regional map (~103 km²) centered at 50.75°E 26.11°N, encompassing the entire plateau and the Montes Agricola.

Methodology: Regional mapping is carried out at a scale of 1:80,000 using a 7 m/pixel mosaic of SELENE (“Kaguya”) Terrain Camera (TC) morning images. Initial identification and digitization of linework and units is conducted on our basemap (Kaguya Terrain Camera) in conjunction with merged LOLA-Kaguya data (topography, hillshade, and slopemap). Further unit characterization and delimitation is also based on numerous other datasets. We will map mineralogic units that lack corresponding morphologic or albedo signatures (e.g., olivine-rich areas on the southeastern rim of Aristarchus or silicic areas in several specific locations) as overlay textures instead of assigning separate units.

Initial results: We identified 45 potential volcanic collapse structures (irregular pits; IRPs; ~0.3 km² to ~110 km² with a mean at ~7 km²). Most of these structures have not been reported in previous investigations and all but six IRPs are located on the Aristarchus plateau. In our map, the term “rille” is defined as linear depression indicating a formation by volcanic drainage, i.e., it has to fulfill two of the following criteria: 1) Sinuous trace; 2) Following the topographic gradient; 3) Connected to or closely associated with an IRP. We mapped a total of 100 rilles with total, maximum, and minimum lengths of 1724 km, 110 km, and 0.5 km, respectively. Additionally, we identified 78 highly degraded rilles and segments, for a total rille length of ~2033 km. We also detected two ~3.7 km long and up to ~24 m high, sinuous ridge segments approaching Rima Krieger. Two more ~2.5 km and ~5 km long sinuous ridges are located north of the Montes Agricola. If these represent inverted rilles, they would triple the number of such features identified on the Moon.