Exploring Lacus Veris, Orientale To Probe The Volcanic And Impact Histories Of The Moon
Fundamental questions about the formation and evolution of the Moon remain unanswered, and access to the lunar surface is critical in order to improve upon current understanding. Key high-priority science goals for lunar origin  include: Goal 1 – constrain the bombardment history of the inner Solar System; Goal 3 – investigate the diversity of lunar crustal rocks; Goal 5 – investigate volcanic materials to constrain the thermal and compositional evolution of the Moon, Goal 6 – investigate impact processes on planetary scales; and Goal 7 – investigate regolith processes and weathering on airless bodies. Significant progress towards addressing these goals can be made in areas where diverse lithologies are observed and accessible on the surface. An example of one such diverse location is Lacus Veris, a mare basalt sea at the foot of the Outer Rook Ring in eastern Orientale basin, the youngest impact basin of its size on the Moon. Lacus Veris is the second-largest mare deposit within Orientale basin. The proposed landing site (Fig. 1a) is in the largest of five ponds 8890 km2 ~1385 km3), emplaced between 3.69 Ga and 3.20 Ga . The mare deposits within Lacus Veris contain medium- to high-Ti basalts (Fig. 1b) and embay highlands material with ~95% plagioclase  that was uplifted from the lunar crust at the time of the Orientale impact. The site of interest (Fig. 1) is located where a sinuous rille crosses a geologic boundary [mare basalt-impact melt (Maunder Formation)]. This site would enable investigations of key NRC science objectives, including: 1) sample mare material to determine composition and absolute age of volcanic activity and to investigate sinuous rille formation (Goals 5 and 7); 2) sample impact melt to determine its composition and the absolute age of the Orientale impact event (Goals 1, 6); and 3) sample anorthositic material at the base of the Outer Rook Ring to determine its composition and shock levels and constrain its depth of origin, thus addressing the formation of rings in large basins (Goals 1, 3). Mobility and in situ sample analyses would be required to take full advantage of the scientific opportunities at this location; returned samples would further enhance the science returned from exploring this location. Additionally, this site is on the boundary between nearside thin crust and farside thick crust , and would extend our analysis of lunar surface materials beyond the Procellarum KREEP Terrain. Investigations at a companion site in western Orientale (see Whitten et al., this meeting) could investigate variations across this crustal thickness boundary.