Modeling the Meteoritic Bombardment of Saturn's Rings to Estimate Their Age
Abstract
The rings of Saturn vary radially in brightness due to a variety of factors such the optical depth of the rings and the ratio of endogenous water ice to non-icy exogenous material, as well as the morphology of the ring particles. The radial optical depth profile, as measured by UVIS stellar occultations (Colwell et al. 2009), provides the filling factor of each of the major regions of the rings. Taking this into account, we perform a meteoritic bombardment simulation, using a Markov Chain based simulation (Elliott and Esposito 2011), which calculates the evolution of the fractional pollution over long time scales. This gives us a fractional pollution time series which we can then compare to the fractional pollution observed by UVIS. In order to calculate the current fractional pollution of the ring system, taking the filling factor into account, we model the UVIS spectra for the A, B and C rings using Hapke's 2012 model for bidirectional reflectance of a surface composed of an intimate mixture of regolith grains. We then perform a non-linear least-squares fit to these spectra with two free parameters, the fractional pollution of the rings and the surface roughness of the particle. UVIS observations at different phase angles are used to constrain the surface roughness. We perform this fit for several different pollutants, and a statistical goodness-of test is performed to assess the quality of each fit. We then compare the Markov-chain model result to the UVIS fit spectrum, which gives us an estimate for the age of the rings.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #50
- Pub Date:
- October 2018
- Bibcode:
- 2018DPS....5011907E