Long-lived volcanism expressed through mare infilling, domes and IMPs in the Arago region of the Moon

Overview & Synopsis

Mare Tranquillitatis corresponds to the deposit of successive Early to Late Imbrian basaltic units filling the Tranquillitatis basin on the Moon. The present study focuses on the western half of the mare, in the vicinity of the Arago crater (6.16°N, 21.42°E). High resolution datasets from recent remote sensing missions were used to reconstruct the geologic history of the area, which includes a variety of geological features such as: 8 extrusive domes, numerous wrinkle ridges, a sinuous rille and 37 Irregular Mare Patches (IMPs). We performed crater counting to date the domes emplacement and estimated the domes lava rheologic properties (plastic viscosities, lava effusion rates, and durations of effusion) using their geometric characteristics. As a result we classify the Arago domes into three groups: E1-type domes (Arago 1 and 8), H1-type domes (Arago 4 to 7), and B-type domes (Arago 2 and 3) respectively emplaced ​~ ​3.7 ​Ga, ~3.4 ​Ga, and ~2.8 ​Ga ago. IMPs are observed in the younger mare unit and on the top of the Arago 6 dome; they likely correspond to a late stage of waning mare volcanism in the area. Both IMPs and domes have a composition similar to the surrounding mare in the VNIR spectral domain, consistent with mafic materials. The exceptionally long-lived volcanism and its diversity recorded in the Arago region may be related to both a Th-rich anomaly reported nearby and to the large-scale magma center responsible for the Lamont positive Bouguer anomaly. In addition, volcanic features of the Arago region are superimposed on a Ti-rich mare unit visited by the Apollo 11 crew 175 ​km to the south at Tranquility Base. The geological and historical richness of this region makes it a compelling site for future science and/or In Situ Resources Utilization (ISRU) driven missions to the Moon.