Influence of adding CO and CO₂ to the ice composition. A: the erosion sustained after ten orbital revolutions for seven facets of pit 5, for various CO and CO₂ abundances: no CO and CO₂, 1% CO and 1% CO₂, and 5% CO and 15% CO₂ from left to right, respectively. B1 and B2: the activity patterns of two facets are given – H₂O production rate on the left, CO₂ and CO production rates in the middle column, and thickness of the dust layer on the right. The activity of facet 1 is quenched in the presence of CO and CO₂. The behavior of facet 2 is given for comparison: it remains active in the presence of CO and CO₂, preventing the formation of a dust layer (right plot).