Ages of Small-Scale Maria in the Poincaré Basin

AGES OF SMALL-SCALE MARIA IN THE POINCARÉ BASIN. A. Starcke, W. Iqbal, C. H. van der Bogert, N. Schmedemann, and H. Hiesinger. Institut für Planetologie, Universität Münster, Wilhelm-KlemmStr. 10, 48149 Münster, Germany ([email protected]) Introduction: An old impact basin like Poincaré is bound to be a geologically diverse region through superposition of newer craters onto the pre-Nectarian basin materials alone. However, the history becomes even more complex due to subsequent volcanic processes. A new geological map of the Poincaré region presented at this year’s LPSC [1] provides a more detailed look into the region’s history compared to previous maps. It shows several small Imbrian-aged dark plains (Idp), interpreted as maria in the study, which either were not individually mapped or were combined with neighboring units. Some of the mare deposits have been previously studied using crater size-frequency distribution (CSFD) analyses to determine their absolute model ages. However, most studies to date based their measurements on Lunar Reconnaissance Orbiter (LRO) Wide-Angle Camera (WAC) data, which has a resolution of ~100 m/pixel. Thus, the CSFDs could only be used to determine ages for units with craters larger than ~500 m in diameter [2]. At this resolution, rugged terrain also prevented the measurement of CSFDs for small mare units [2]. Higher resolution data such as Kaguya or Narrow-Angle Camera (NAC) imagery can provide a closer look at these areas (Fig. 1). However earlier studies using Kaguya data (~10 m/pixel), only differentiated between three distinct maria within the Poincaré basin [3], while newer WAC based studies identified about 12 maria [2]. Our new project aims to investigate CSFDs of more of the small-scale maria in the Poincaré basin using NAC imagery to provide more detailed information about the mare units. Of particular interest are the maria along the proposed path of the Endurance mission concept study, which has two planned sampling sites on Poincaré’s maria [4]. Method: We will determine absolute model ages for the three mare patches within Poincaré basin that are crossed by the Endurance route using CSFDs on a NAC mosaic with a resolution of 2 m/pixel. Expected results: The results of this project are expected to fit into the known range of the region’s ages of 3.13-3.42 Ga of the inner basin floor mare unit [2,3]. Younger ages may be revealed due to the examination of smaller areas, which could have experienced small amounts of late basalt emplacement, as seen for example at the Chang’e-6 landing site [5]. References: [1] Hiesinger et al. (2025) LPSC 56. [2] Pasckert et al. (2017) Icarus 299 (2018) 538-562. [3] Haruyama et al. (2009) Science 323.5916 (2009): 905–908. [4] Keane et al. (2021) https://smdcms.nasa.gov/wp/content/uploads/2023/11/enduranc e-spa-traverse-and/sample-return.pdf. [5] Gao et al. (2025) Journal of Geophysical Research Planets 130, e2024JE008658. Figure 1: Mare deposit in the outer ring of Poincaré basin. Complex terrain, including the presence of secondary crater materials, has hindered CSFD measurements previously.