Iron Depletion in Silicates of Saturn’s Main Rings
- 1Institute of Geological Sciences, Freie Universität Berlin, Germany (s.linti@fu-berlin.de)
- 2Laboratory for Atmospheric and Space Physics, University of Colorado-Boulder, USA
- 3Institute of Earth Sciences, Heidelberg University, Germany
- 4Space Physics and Astronomy Research Unit, University of Oulu, Finland
Measurements during the final phase of the Cassini mission revealed the composition of individual dust particles, ejected by micrometeoroid impacts from Saturn’s main rings. These measurements were conducted with the in situ time-of-flight mass spectrometer of the Cosmic Dust Analyzer (CDA) [1] during the close planet encounters of the Grand Finale Orbits from April to September of 2017.
Here we present the compositional analysis of silicate bearing nanoparticles (about 20–100 nm in radius), that, according to our dynamical models [2], are ejected mainly from the B and C rings by micrometeoroid impacts. With an observed ice-to-silicate particle ratio of 2:1 [2], we see a much higher silicate abundance in these ring segments, compared to values constrained by remote sensing techniques [3,4,5].
In order to assess the elemental composition of individual particles, application of a deconvolution technique to the CDA mass spectra is required. This technique is based on an approach to constrain the composition of Interstellar Dust Particles (ISDs), also detected with CDA [6]. After application of the deconvolution and Relative Sensitivity Factors (RSFs) [7], elemental abundances for the individual particles are derived.
We find Mg, Si and Ca similar to cosmic abundances (ISD and CI chondritic). Fe, however, is significantly depleted, for the Fe/Mg ratio on average by a factor of 2.3 compared to cosmic abundances. This observation contrasts with Fe-rich (≈ 5 w.r.t. cosmic abundances) exogenous material (IDPs), observed in the Saturnian system by CDA [8]. This drastic discrepancy in composition between ring silicates and IDPs at Saturn seems difficult to reconcile with IDPs being the main factor in polluting and darkening the rings over time [4,5,9,10]. We review several scenarios, how these compositional differences could be explained.
References
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How to cite: Linti, S., Hsu, H.-W., Fischer, C., Trieloff, M., Hillier, J., Schmidt, J., and Postberg, F.: Iron Depletion in Silicates of Saturn’s Main Rings, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-367, https://doi.org/10.5194/epsc2022-367, 2022.
