Comparison of the emission spectra of 3I/ATLAS with those of a typical comet (103P/Hartley 2; Y. Shinnaka et al. 2013) in the wavelength region covering the NH₂ (0,8,0) band and the [O I] emission lines at 630 and 636.4 nm. The subpeak at 633.4 nm, corresponding to the red half of the NH₂ (0,8,0) band, is very weak or absent in 3I/ATLAS, suggesting that NH₂ is depleted with respect to [O I] (used here as a proxy of H₂O). The blue-side wing of the [O I] emission line at 630 nm in 103P/Hartley 2, around 628 nm, is a part of the NH₂ (0,8,0) band (see also Figure 2(i)n (Y). Shinnaka et al. 2013 or Figure 3 in Y. Kanda et al. 2008 for more detail).

(The data used to create this figure are available in the online article.)

(The data used to create this figure are available.)