  Not only do the sampled terrestrial worlds (Earth, Mars, and asteroid 4
Vesta) differ in their mass-independent (nucleosynthetic) isotopic compositions
of many elements (e.g. $\varepsilon^{48}$Ca, $\varepsilon^{50}$Ti,
$\varepsilon^{54}$Cr, $\varepsilon^{92}$Mo), the magnitudes of some of these
isotopic anomalies also appear to correlate with heliocentric distance. While
the isotopic differences between the Earth and Mars may be readily accounted
for by the accretion of mostly local materials in distinct regions of the
protoplanetary disc, it is unclear whether this also applies to asteroid Vesta.
Here we analysed the available data from our numerical simulation database to
determine the formation location of Vesta in the framework of three
planet-formation models: classical, Grand Tack, and Depleted Disc. We find that
Vesta has a high probability of forming locally in the asteroid belt in models
where material mixing in the inner disc is limited; this limited mixing is
implied by the isotopic differences between the Earth and Mars. Based on our
results, we propose several criteria to explain the apparent correlation
between the different nucleosynthetic isotopic compositions of the Earth, Mars,
and Vesta: (1) these planetary bodies accreted their building blocks in
different regions of the disc, (2) the inner disc is characterised by an
isotopic gradient, and (3) the isotopic gradient was preserved during the
formation of these planetary bodies and was not diluted by material mixing in
the disc (e.g. via giant planet migration).
