IN-SITU PETROLOGIC AND REGOLITH CLUES: ASSESSING IRREGULAR MARE PATCH HYPOTHESES THROUGH LANDER AND ROVER CAMERAS ON DIMPLE

The DIMPLE (Dating an Irregular Mare Patch with a Lunar Explorer) payload will establish the age and lithology of the Ina lunar Irregular Mare Patch (IMP). DIMPLE (Anderson et al., 2024) will fly within NASA’s Payloads and Research Investigations on the Surface of the Moon (PRISM) program as part of the Commercial Lunar Payload Services (CLPS) initiative. It will analyze samples on the lunar surface with the Chemistry, Organics, and Dating EXperiment (CODEX) (Levine et al., 2023), operating two mass spectrometers: laser-ablation (elemental abundances) and resonance-ionization (Rb, Sr isotopic abundances). DIMPLE will also utilize images from cameras on the CLPS lander and rover to obtain a more complete understanding of Ina, with implications for other IMPs.

Several hypotheses aim to explain IMP unusual morphology, and each have predictions for age, chemistry, and/or petrologic texture. Images will provide textural information from samples (e.g., grain size, vesicularity) to help determine the formation process. The lander camera will provide close-up images of samples prior to analysis. Rover camera images will be used to select samples to carry to the lander and to examine local materials (e.g., rocks, partially buried boulders). Small, recent (<100 Ma) basaltic eruptions may be fine-grained (Braden et al., 2013, 2014; Boyd et al., 2024), but small intrusions within the collapse caldera may be coarse-grained (El-Baz, 1972, 1973; Strain & El-Baz, 1980). In contrast, lava flow inflation (Garry et al., 2012), lava lake processes, and magmatic foam extrusion hypotheses (Qiao et al., 2017, 2018, 2019; Wilson & Head, 2017; Vannier et al., 2024; Gao et al., 2024) predict vesicular material. If Ina were old, but the ancient surface regolith were removed by episodic, recent (<10 Ma) outgassing (Schultz et al., 2006; Vannier et al., 2024), exposing previously buried basalts, the samples may be massive, rather than vesicular.

Other information can be gathered from the regolith. For example, photometric analyses suggest Ina’s rough floor units may be covered by black glass beads such as found at Apollo 17 (Boyd et al., 2024) – will DIMPLE identify an abundance of these materials? Regolith thickness and physical properties can be also be inferred from observations of wheel-tracks, depth of sinking for the lander footpads, and depth of small impact craters not resolvable from orbital data.