TPD curves of each component in experiments a) E1-E5 (pure ices); b) E10 (pre-cometary ice mixture with heating rate = 2 K/min). Desorption of a molecule with mass fragment m/z = 15 at T < 60 K does not correspond to NH₃, since that feature is not shared with the m/z = 17 fragment (not shown for clarity), and it may be due to a contaminant; c) E11 (pre-cometary ice mixture with heating rate = 1 K/min). Temperatures of desorption peaks are indicated. Ion current in the y-axis corresponds approximately to the partial pressure (mbar) in the main chamber. Note that the y-axis is on a logarithmic scale.