Mixing ratio profiles of H₂O, CO, and CO₂ obtained when a production rate due to ice grain ablation for every species with integrated rates of 6.0 × 10⁴, 2.45 × 10⁴ and 4.5 × 10³ cm⁻² s⁻¹ is taken into account. An additional source of cometary CO is considered as well, the impactor size is D = 2 km, and the evolution time needed to match the Herschel observations is 639 yr. The red dashed line refers to the carbon monoxide profile resulting from the simulation of case 2 (see Table 4).