I don't understand. If "theia" hit earth and formed moon, why would the istopic signatures be any different. Now both earth and moon come from same pair of different objects.
We would expect different proportions of the isotopes on the Earth and the Moon. This is because the Moon according to the models would have a greater proportion of its mass made up of the theorised collider "Theia" than Earth.
In this particular experiment they showed the isotopic proportions matched between here and the Moon.
