The red outline belongs to the CO ice sublimation case, while the blue one is for CH4. In both cases the properties of the dust layer are the same with a thickness of 5 cm and Ra = 10−6 m. It takes about 0.9 Myr to reach the volume of SHAPE-ORIG when CO is the major volatile species, while about 3.1 Myr for CH4 ice sublimation. In the left panel the results are shown as cross-sections through equatorial and polar regions. In the right panel we show the final 3D body with color scale denoting radial differences between facet centers of the two cases (CH4 minus CO case). From the point of view of the flattening process of the two lobes we conclude that the results are nearly identical, hence, independent of the type of ice in question. However, a faster volume loss due to higher CO volatility produces less erosion in the polar regions but higher at the equatorial areas in the time it takes to reach the SHAPE-ORIG volume. The principle of this effect follows from the fact that the CO to CH4 volatility in the less illuminated equatorial region is higher than the time ratio needed to reach the final shape, which is not the case for areas under nearly constant illumination.