Maximum likelihood surfaces for inheritance scenario, for full sample of molecular species. The maximum likelihood increases from dark purple contours to light green contours. Darkest purple contour represents maximum likelihood of 10⁻⁴, and increases with each lighter contour level to 3 × 10⁻⁴, 10⁻³, 3 × 10⁻³, 10⁻², 3 × 10⁻², 10⁻¹, and finally 3 × 10⁻¹ for the lightest green contour. Radius in AU in the physically evolving protoplanetary disk midplane is on the x-axis, and evolution time in Myrs is on the y-axis.