Also, a recent paper shed some doubt on the impact theory (apparently Earth and Moon isotopes are too similar), so the impact might not have happened or it might have been different than previously thought (glancing and causing the proto-Earth to spin itself apart, or strong enough to completely melt and mix both objects).
In any case, though, yeah, Mars has the wrong composition, size, and orbit for it to have been involved in any impact with Earth. The mistake probably came from Theia often being described as ‘Mars sized’.
No, Mars was not formed by the moom-forming impact event between Gaia and Theia. The moon is the remnant you’re talking about, not Mars.
Also, a recent paper shed some doubt on the impact theory (apparently Earth and Moon isotopes are too similar), so the impact might not have happened or it might have been different than previously thought (glancing and causing the proto-Earth to spin itself apart, or strong enough to completely melt and mix both objects).
In any case, though, yeah, Mars has the wrong composition, size, and orbit for it to have been involved in any impact with Earth. The mistake probably came from Theia often being described as ‘Mars sized’.