The DIMPLE Experiment to Date Ina, a Young-Looking Volcanic Structure on the Moon
- 1Southwest Research Institute, Boulder, CO 80302 USA
- 2Lockheed Martin Space, Littleton, CO 80127 USA
- 3Lunar Scholar Services LLC, Aurora, CO 80247 USA
- 4Western Carolina University, Cullowhee, NC 28723 USA
- 5Universität Bern, CH-3012 Bern, CH
- 6Brown University, Providence, RI 02912 USA
- 7The University of Manchester, Manchester M13 9PL, UK
- 8Colgate University, Hamilton, NY 13346 USA
The DIMPLE (Dating an Irregular Mare Patch with a Lunar Explorer) experiment has been selected by NASA for flight to the Moon later this decade. The objective is to date volcanic rocks from Ina, the largest known (3×2 km) irregular mare patch. Ina is remarkable for its scarcity of impact craters; taken at face value, the crater density implies a surface model age of 33 ± 2 Ma [1]. If the Moon was volcanically active this recently, it would require a profound reassessment of our understanding thermal evolution of the lunar interior. An alternative explanation for the anomalously low crater density posits that Ina is a chilled magmatic foam [2], the vesicularity of which favors crumbling rather than cratering during meteoroid impacts. If vesicularity can make a ~3000 Ma old terrane appear to be 100× younger, it begs the question of what other surface age estimates based on crater density, from anywhere in the inner Solar System, can also be wildly inaccurate.
The DIMPLE payload includes (i) the CODEX (Chemistry, Organics, and Dating Experiment) instrument, (ii) a sample-handling system including an arm for gripping rocks off the lunar surface, and (iii) a rover-mounted rake for collecting rock samples from farther afield. CODEX works by analyzing hundreds of 35 μm spots over rock samples 1.9-3.8 cm across, using laser-ablation mass spectrometry to measure the abundances of major elements and some trace elements, and using laser-ablation resonance-ionization mass spectrometry to measure the isotopic abundances of Rb and Sr. In this lunar context, the organics capability of CODEX will not be exploited. The mass spectrometer for CODEX is a re-flight of the mass spectrometer designed for the Luna-Resurs mission, with an optimized ion source to collect resonantly excited ions in addition to ions produced directly by laser ablation. CODEX data will enable dating by the 87Rb-87Sr isochron technique and, by mapping elemental composition, will permit lithologic classification and petrologic interpretation of the analyzed rock samples from Ina.
References: [1] Braden S.E. et al. (2014) Nature Geoscience 7, 787.
[2] Qiao L. et al. (2021) Planet. Sci. J. 2 66.
How to cite: Anderson, F. S., Bierhaus, E. B., Braden, S. E., Fagan, A. L., Fausch, R. G., Head III, J. W., Joy, K. H., Levine, J., Osterman, S., Pernet-Fisher, J., Tartèse, R., Wurz, P., and Yant, M.: The DIMPLE Experiment to Date Ina, a Young-Looking Volcanic Structure on the Moon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13507, https://doi.org/10.5194/egusphere-egu24-13507, 2024.
