And correct me if I'm wrong, here, but don't we only have a very small amount of meteorites known to have come from the Moon, and didn't we identify them as such because of their similarity to Apollo samples, meaning they couldn't possibly be the source anyway?
No lunar meteorites were identified as such before the Apollo and Luna. Indeed it as their similarity to Apollo and Luna samples that led them to be identified as such and identifiability distinct from other achondritic meteorites such as SNCs (Mars) and HEDs (Vesta). The first lunar meteorite was not discovered until 1979 and the first recognised in 1982.
I'm curious though. Since we don't have any Martian samples, how do we know those meteorites are from Mars then? One of those things I've always been curious about.
Classic case of inductive reasons and a process of elimination.
The SNC meteorites are a family of achondritic meteorites (they are essentially mafic rocks similar to terrestrial examples.) with specific geochemical characteristicscommon to all.
The SNCs have undergone melting. So they have to have come from a silicate body with volcanism. This means Mercury, Venus, Earth, Moon, Mars, Vesta, and Io.
Earth, Moon, and Vesta are eliminated by stable isotope data.
Venus and Io are delineated by unreason energy requirements to be sent on Earth intersecting orbits. Mercury isn not quite ruled out, but is unlikely.
The Viking landers measured the noble gas isotopes in the martian atmosphere. The noble gas isotopes in the SNCs match these.
So Mars is the obvious choice.
This is the argument used by the initial researcher Or you can use the following argument from me:
The parent body had to be one that is of silicate composition. That rules out all but the terrestrial planets and Io.
The parent body has to have had a long history of volcanic activity (from four billion years ago to a few hundred million years ago. This rules out Mercury, the Moon, Vesta.
The parent body had to have free water on its surface (there is aqueous alternation in most SNCs. This rules out Venus and Io.
The great age of some SNCs rules out Earth.
Mars is the only one left. If it did not exist it would have to be invented.