P035-0004
Surface temperature and the compositional effects of electron bombardment on Dione

Thursday, 10 December 2020
Poster
Cindy Young1, Michael S Grant1, Conor A Nixon2, Francesca Scipioni3, Tom Nordheim4, Jason Campbell Cook5 and Tanner Hayes6, (1)NASA Langley Research Center, Hampton, VA, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)SETI Institute, Mountain View, CA, United States, (4)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (5)Pinhead Institute, Telluride, CO, United States, (6)University of Nevada Reno, Reno, NV, United States
Abstract:
Saturn’s icy moons are composed primarily of water ice with minor other “contaminants,” such as CO2 ice and a dark component thought to be organics, hematite and/or metallic Fe [1]. The space weathering process of electron bombardment is expected to be particularly important on the surfaces of Saturn’s inner moons (Mimas, Tethys, Dione, and Rhea), as they orbit within Saturn’s inner magnetosphere. Terrains exhibiting thermal anomalies (i.e., colder temperatures in the day and warmer temperatures at night than surrounding areas) correspond to regions of high energy electron bombardment [2; 3; 4; 5]. Energetic electrons impact the surfaces, sintering ice grains together, and this process becomes more effective for increasing particle energies [6]. Solar UV radiation, cosmic rays, dust in-fall, and cold plasma particles trapped in Saturn’s magnetic field also play an important role in altering the nature and the structure of the native surface ices by the implantation of contaminants, ionization, sputtering, and dissociation of water ice molecules [7]. Additionally, CO2 could be sourced from irradiation of dark organic material [8]. Many of these surface alterations are observable in Cassini’s Visible and Infrared Mapping Spectrometer (VIMS) spectra [9]. We used similar methodologies as have been employed in previous works [e.g., 10] to derive surface temperatures from Cassini’s Composite Infrared Spectrometer (CIRS), which helped to isolate areas where space weathering due to electron bombardment is more predominant. The subtle changes in VIMS spectra were investigated using machine learning techniques. We present here our results for Dione.

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[9] Scipioni, F., et al. (2017) Icarus, 290, 183-200

[10] Howett, C. J. A., et al. (2014) Icarus, 241, 239-247

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