Lunar Xenon and the Origin of the Indigenous Component

Lunar indigenous Xe isotopic abundances provide crucial information on relationships not only between gas reservoirs in the solar protoplanetary disk but also regarding planetary fractionation processes and possible space weather effects due to an active young Sun. The indigenous lunar Xe isotopic composition is not yet firmly established. A verification of previously inferred lunar Xe signatures using rocks of varying compositions from Apollo 16 and 17 missions is made here. Ancient lunar highland rocks carry cosmic-ray-produced spallation and neutron-capture products, fission components due to Pu-244 and U-238, as well as terrestrial contamination gas, all complicating the identification of the indigenous lunar Xe component. The present study reveals light and heavy isotopic abundances compatible with terrestrial Xe composition. We conclude that in order to firmly establish indigenous lunar Xe signatures in situ, Xe measurements on the moon in interior samples of anorthositic ejecta from very recent craters should be performed.