3,- 1SETI Institute, Mountain View, CA, United States of America (jspitale@seti.org)
- 2Tierra Right of Way Services, Tucson, AZ, United States of America
- 3California Institute of Technology, Pasadena, CA, United States of America
- 4Southwest Research Institute, Boulder, CO, United States of America
- 5NASA Goddard Space Flight Center, Greenbelt, MD, United States of America
- 6Diné College, Tsaile, AZ, United States of America
We map surface eruptive activity in Cassini images of Enceladus' south-polar terrain (SPT) at fifteen epochs spanning late 2009 to late 2015 using a refined curtain approach derived from that of our earlier work [1]. This refined approach gives a better representation of the uncertainties in identifying source fractures by allowing for multiple candidate sources to be identified for an observed eruption. Our analysis includes the five epochs studied in [1], which were independently re-examined here. Our results are summarized in Figure 1. About 80% of the currently active fracture system in the SPT (by length) was observed to be erupting at a level detectable in Cassini images during every epoch. On/off variability is observed almost exclusively at the fringes of the fracture system, possibly reflecting a thickening ice shell away from the pole. No definitive connection between surface activity and the roughly factor-of-three plume optical depth variation with mean anomaly [2,3] is made here, but our results do not rule out a scenario where the pattern of eruptive activity on the surface is correlated with mean anomaly, provided only the fractures at the fringe of the SPT ever turn completely off during the tidal cycle. Our results are best explained by eruptions sourced directly from the ocean.
Figure 1. a) Averaged eruptive activity. At each point, the intensity represents the number of times the point was determined to be active divided by the number of times it was observed (i.e., determined to be either active or inactive). Indeterminate and degenerate points are not counted, except in cases where two fractures are so close to one another as to be effectively indistinguishable. b) Number of observations used for each average in (a). c) Standard deviation at each point in (a). Blue points have zero standard deviation. (from [4])
References:
[1] Spitale et al. 2015; Nature 521
[2] Hedman et al. 2013; Nature 500
[3] Nimmo et al. 2014; AJ 148
[4] Spitale et al. 2025; PSJ 6:67
How to cite: Spitale, J., Tigges, M., Berne, A., Rhoden, A., Hurford, T., and Webster, K.: Inferred Eruptive Activity in Enceladus' South-Polar Terrain from Cassini ISS, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-829, https://doi.org/10.5194/epsc-dps2025-829, 2025.
