EVALUATION OF AGE AND RHEOLOGY AS THE CAUSES OF THE MORPHOLOGICAL DISTINCTIVENESS OF AHUNA MONS ON (1) CERES.

Dawn mission data of (1) Ceres shows evidence of cryovolcanic activity in the form of dome-like structures, the most prominent is the mountain Ahuna Mons. Morphologically, Ahuna Mons shows characteristics consistent with a volcanic dome including a high aspect ratio and sharp features revealing a distinct dome-like shape. Other possible domes were identified, but have significantly lower aspect ratios and weaker, degraded features. If Ahuna Mons and the other domes are cryovolcanic in origin, one possibility for the morphology difference may be that Ceres’ cryovolcanic domes are ice-rich and viscously relax over geologic timescales. In this study, we investigated two hypotheses to ascertain the cause of differences between Ahuna Mons and candidate domes: 1) Ahuna Mons is different morphologically because of a difference in age, or 2) Ahuna Mons is different morphologically because of a difference in rheology (ice content). We used crater counting to determine dome age and measured dome aspect ratios to compare and to determine any correlations. A moderate (0.4 ≤ r < 0.7) to strong (r > 0.7) inverse correlation between aspect ratio and dome age would support hypothesis 1. A weak correlation (r < 0.4), or no correlation, would support hypothesis 2. Our results do not show significant correlations between age and aspect ratio which supports hypothesis 2 indicating Ahuna Mons differs from other domes because of its ice content. Our results are consistent with a lateral variation in ice content across Ceres’ surface. Furthermore, we also find a possible ~100 Myr age gap between Ahuna Mons and all but one of the low aspect ratio domes, suggesting that ice content may vary over time on Ceres.