Constraining the magmatic evolution of the Moon with Pb isotope measurements of lunar basalts

The formation and the evolution of the Moon is not yet fully understood by the scientific community. Therefore, analysis of lunar samples is crucial to understand how the Moon evolved through time.

Photo: False color element map of a lunar basalt collected during the Apollo 12 mission. Credit: Renaud Merle

Project overview

The overall purpose of this project is to characterize and date (with different isotopic systems) Moon samples collected by Apollo missions as well as lunar meteorites found on Earth to better understand the formation and evolution of the Moon.

Project description

The most widely accepted model for the formation of the Moon is that it originated from the debris generated during a giant impact between a Mars-sized body and the early Earth. It is thought that the heat produced as this debris accreted resulted in the formation of a global “magma ocean” covering the surface of the Moon.

The cooling and crystallization of this magma ocean led to the formation of the lunar crust and the reservoirs of material in the lunar mantle that would be subsequently erupted onto the Moon’s surface.

We have developed a new approach for determining precise crystallization ages of the lunar basalts that formed in these volcanic eruptions, by analyzing their lead (Pb) isotopic compositions using Secondary Ion Mass Spectrometry (SIMS). We are using these ages and isotopic compositions to construct a model that will help us to understand the sources of lunar volcanic activity, the evolution of the lunar magma ocean and, ultimately, when the Moon itself was formed.

Funding

Vetenskapsrådet (The Swedish Research Council)

Selected publications

· Snape J. F., Nemchin A. A., Bellucci J. J., Whitehouse M. J., Tartèse R., Barnes J. J., Anand M., Crawford I. A. and Joy K. H. (2016): Lunar basalt chronology, mantle differentiation and implications for determining the age of the Moon. Earth Planet. Sci. Lett. 451, 149-158 (http://dx.doi.org/10.1016/j.epsl.2016.07.026 External link.)

· Snape, J.F., Davids, B., Nemchin, A.A., Whitehouse, M.J. and Bellucci, J.J., 2018. Constraining the timing and sources of volcanism at the Apollo 12 landing site using new Pb isotopic compositions and crystallisation ages. Chemical Geology, 482, pp.101-112 (https://doi.org/10.1016/j.chemgeo.2018.02.009 External link.)

· Snape, J.F., Nemchin, A.A., Whitehouse, M.J., Merle, R.E., Hopkinson, T. and Anand, M., 2019. The timing of basaltic volcanism at the Apollo landing sites. Geochimica et Cosmochimica Acta, 266, pp.29-53 (https://doi.org/10.1016/j.gca.2019.07.042 External link.)

· Merle, R.E., Nemchin, A.A., Whitehouse, M.J., Snape, J.F., Kenny, G.G., Bellucci, J.J., Connelly, J.N. and Bizzarro, M., 2020. Pb‐Pb ages and initial Pb isotopic composition of lunar meteorites: NWA 773 clan, NWA 4734, and Dhofar 287. Meteoritics & planetary science, 55(8) (https://doi.org/10.1111/maps.13547 External link.)