Extended Data Fig. 4: Example CDA spectra from individual HMOC-type ice grains. | Nature

Extended Data Fig. 4: Example CDA spectra from individual HMOC-type ice grains.

From: Macromolecular organic compounds from the depths of Enceladus

Extended Data Fig. 4

In these individual spectra, the peak definition is naturally higher than in the co-added spectra shown in Fig. 1 and Extended Data Fig. 3, and therefore some of the spectral features collected in Fig. 1b become more apparent. a, HMOC spectrum from one of the fastest recorded impacts (12–18 km s−1). The appearance of hydrogen cations (H+, \({{\rm{H}}}_{2}^{{\rm{+}}}\) and \({{\rm{H}}}_{3}^{{\rm{+}}}\)) at 1 u, 2 u and 3 u, as well as the disintegration of the \({{\rm{CH}}}_{{\rm{3}}}^{{\rm{+}}}\) ion into \({{\rm{CH}}}_{2}^{{\rm{+}}}\), CH+ and C+ (12 u–15 u) and the formation of H2O+ (18 u), are evidence of the high-speed impact. The abundance of unsaturated small cations below 70 u, probably fragments from aromatic structures, is increased compared to slower spectra. The frequently occurring mass line at 45 u (Fig. 1b and Extended Data Fig. 1) is noticeable; it cannot originate from pure hydrocarbons and requires heteroatoms, probably oxygen in this case. While a 45 u feature is quite common in our HMOC dataset, the peak at 86 u is only apparent in this spectrum. b, HMOC spectrum from a grain detected at intermediate speed (5–8 km s−1). High-mass fragments and benzene species are abundant whereas further fragmentation of the benzene ring into C5 and C4 species is less apparent compared to high-velocity impacts (a). We note that organic cations with 2, 3, 4 and 5 C atoms show a tendency to carry more H atoms compared with the high-speed impact, which is indicative of ‘softer’ ionization from the slower impact. Organic fragmentation below \({{\rm{CH}}}_{{\rm{3}}}^{{\rm{+}}}\) is usually not observed in this speed regime.