Calcium (⁴⁸Ca), titanium (⁵⁰Ti), chromium (⁵⁴Cr), and molybdenum (⁹²Mo) isotopic anomalies for Earth, Moon, Mars, and Vesta (sampled by the HED meteorites) plotted with respect to their distance from the Sun. The isotopic compositions of these planetary bodies appear to correlate with their semi-major axes, alluding to the presence of isotopic gradients in the inner Solar System (e.g. Trinquier et al. 2009; Yamakawa et al. 2010); the data are from the compilation of Dauphas (2017) and references therein. The e⁹²Mo value for Mars is from Burkhardt et al. (2021), while the value for HED is plotted using data for Mesosiderites sourced from Dauphas et al. (2002) because there are no known Mo measurements for HED meteorites to date. There are also no known Mo measurements for the Moon.