Table 2. Table of predictions observed or not observed on Mars.

Predictions for the different proposed sources of 330- to 350-nm luminescence based on laboratory analog instruments. Rows represent the four most important hypotheses for the sources of 330- to 350-nm luminescence considered in this study. Columns show expected wavelength position of the maximum intensity (λ_max), expected band shapes from measurement of standards so far, expected correlation trend with P₂O₅, expected correlation trend with phosphate Raman peaks, and expected correlation trend with Raman G-band for each of the hypothesized sources. Observations made on Mars with the SHERLOC and PIXL instruments are shown in bold font, while observations not made on Mars are shown in normal font. Observations that are partially but not fully fulfilled are shown in bold with a corresponding footnote. Observations that require recommended additional work for a comprehensive evaluation are shown in italics.

Potential sources (type 1 lum.)	λmax (nm)	Raman G-band	Spatial correlation with P2O5 abundance	Spatial correlation with phosphate Raman peak	Band shape components at SHERLOC resolution
Organic	~330–350	Present for ~>0.1 wt % carbon	High-intensity luminescence without P2O5 correlation	High-intensity luminescence without phosphate detection correlation	Any lum. shape that cannot be explained by Gaussian doublet (including but not limited to vibronic bands or positive slope)
Ce3+ in phosphate	~330–350	Should not be present	Statistically significant correlation between luminescence and P 2 O 5	Statistically significant correlation between phosphate Raman peaks and luminescence	Asymmetric Gaussian shape indicate ~340-nm and ~360-nm Gaussian doublets
Potential sources (type 2 lum.)	λmax (nm)	Raman G-band	Spatial correlation with silica and aluminosilicates	Spatial correlation with mineral Raman peaks	Band shape components at SHERLOC resolution
Organic	~280–300*	Present for ~>0.1 wt % carbon	Can be present with silica/silicates but no correlation would strongly indicate organics*	Luminescence correlated to other minerals than silica/silicates†	Any lum. shape that cannot be explained by Gaussian singlet (including but not limited to vibronic bands or positive slope)
Silica/silicate defect	270–290	Should not be present	Exclusive presence of luminescence with silica/aluminosilicate	No observation of correlated Raman peaks because silica and silicate primary modes are outside the Raman wavelength	Gaussian singlet

*These criteria are partially fulfilled.

†One exception found in the Garde rock (fig. S7); however, no PIXL data are available for investigation of co-occurring silica/silicate phases.