Table 2
Compositional constraints for the crater floors (f) and ejecta blankets (e) of the dune and plain craters given by percentages of the six main constituents (H2O, NH3, CO2, CH4 -like, tholin-like, and dark material).
| Dune craters | Ksa | Selk | Santorini | Guabonito | ||||
| Unit | f | e | f | e | f | e | f | e |
| Tholin | 16% | 47% | 21% | 36% | 30% | 42% | 13% | 40% |
| (± 4%) | (± 13%) | (± 6%) | (± 13%) | (± 5%) | (± 11%) | (± 3%) | (± 11%) | |
| Dark material | 84% | 53% | 79% | 64% | 70% | 58% | 87% | 60% |
| (± 7%) | (± 15%) | (± 8%) | (± 15%) | (± 8%) | (± 13%) | (± 10%) | (± 15%) | |
| H2O | – | – | – | – | – | – | – | – |
| CH4-like | – | – | – | – | – | – | – | – |
| NH3 | – | – | – | – | – | – | – | – |
| CO2 | – | – | – | – | – | – | – | – |
| Emissivity | 0.92 | 0.93 | 0.93 | 0.85 | 1 | 0.95 | 0.98 | 0.95 |
| Degradation state | well-preserved | intermediate | degraded | degraded | ||||
| Plain craters | Forseti | Afekan | Soi | |||||
| Unit | f | e | f | e | f | e | ||
| Tholin | 53% | 46% | 54% | 50% | 80% | 82% | ||
| (± 17%) | (± 15%) | (± 15%) | (± 13%) | (± 16%) | (± 15%) | |||
| Dark material | 27% | 24% | 31% | 30% | – | – | ||
| (± 8%) | (± 7%) | (± 7%) | (± 10%) | |||||
| H2O | 20% | 30% | 15% | 12% | 20% | 18% | ||
| (± 5%) | (± 5%) | (± 3%) | (± 3%) | (± 5%) | (± 5%) | |||
| CH4-like | – | – | – | 8% | – | – | ||
| (± 2%) | ||||||||
| NH3 | – | – | – | – | – | – | ||
| CO2 | – | – | – | – | – | – | ||
| Emissivity | 0.93 | 0.83 | 0.95 | 0.93 | 0.93 | 0.90 | ||
| Degradation state | intermediate | intermediate | degraded | |||||
| Special cases | Menrva | Sinlap | ||||||
| Unit | f | e | f | e | ||||
| Tholin | 82% | 83% | 15% | 22% | ||||
| (± 19%) | (± 18%) | (± 4%) | (± 5%) | |||||
| Dark material | – | – | 65% | 53% | ||||
| (± 6%) | (± 13%) | |||||||
| H2O | 18% | 17% | 20% | 15% | ||||
| (± 5%) | (± 4%) | (± 5%) | (± 5%) | |||||
| CH4 -like | – | – | – | 10% | ||||
| (± 3%) | ||||||||
| NH3 | – | – | – | – | ||||
| CO2 | – | – | – | – | ||||
| Emissivity | 0.90 | 0.87 | 0.84 | 0.85 | ||||
| Degradation state | well-preserved | well-preserved | ||||||
Notes. The associated error under each percentage corresponds to the uncertainty of the abundances of the component within the mixtures. The microwave emissivity measurements from the Cassini RADAR radiometry data set are provided in Werynski et al. (2019) and shown in Fig. 1c. As in Werynski et al. (2019), we interpret the low emissivity values (<0.90) to be consistent with an enrichment in water ice and the high emissivity values (>0.95) with an enrichment in organic materials in the top decimeter of the regolith. The relative degradation state is taken from information in Neish et al. (2013, 2018), and Werynski et al. (2019).
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