Distribution and nature of CO2 on Enceladus
Abstract
We present the first global mapping and analysis of CO2 on the surface of Enceladus, and we report the largest concentrations of free CO2 on the southern polar region using the Visual and Infrared Mapping Spectrometer (VIMS) on Cassini. Free CO2 ice and complexed CO2 were already reported near the South Pole (Brown et al., Science, 2006; Hansen, LPSC, 2010). Our work focuses on determining the amount, location and molecular state of CO2 on Enceladus, which could help identify and model geophysical processes that currently occur in the interior. One hypothesis for bringing heat and chemicals to the surface is a warm subsurface ocean containing dissolved gases, mostly CO2 (Postberg F. et al., Nature, 2009). Therefore, our observations are consistent with erupted and condensed materials onto Enceladus' surface (Matson et al., Icarus, 2012; Matson et al. AGU Fall meeting 2015). Free CO2 ice absorbs at 4.268 µm (Sandford and Allamandola, 1990) and CO2 complexed with other molecules absorbs at 4.247 μm (Chaban et al., Icarus, 2007). The Enceladus case is complicated because both free and complexed CO2 are present, and the absorption band of interest is shallow and close to the instrument detection limit. Many of the few Enceladus VIMS data sets have significant and sometimes unusual noise, which we attempted to avoid or remove. We utilized all VIMS data sets available that were collected over ten years of the Cassini mission as a way to improve the detection statistics and signal to noise. We also used wavelengths near 2.7 μm where CO2 has a narrow absorption as a filter to help identify CO2-rich areas. Finally, we selected observations that have spatial resolution better than 100 km in order to create a map that can be compared with the largest fractures, known as Tiger Stripes, in the southern polar region.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2015
- Bibcode:
- 2015AGUFM.P23D..05C
- Keywords:
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- 6099 General or miscellaneous;
- PLANETARY SCIENCES: COMETS AND SMALL BODIES;
- 6218 Jovian satellites;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6299 General or miscellaneous;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 5499 General or miscellaneous;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS