Semi-major axis distribution under the interaction of Venus and Earth. The semi-major axis histogram is given for the cases of all planets present (also indicated by the grey area) and either Earth or Venus absent for β = 0.03 (top) and β = 0.01 (bottom). Vertical dashed lines indicate the locations of several first order as well as the co-orbital MMRs (including a shifting factor to account for radiation pressure). A significant impact on the efficacy of resonances in the region between Earth and Venus is evident, becoming more pronounced at a lower β.