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Maps of Tethys' Thermophysical Properties
C J A Howett1, J R Spencer1, T Hurford2
1- Southwest Research Institute, Boulder, CO 80302, USA.
Icarus
|October 2, 2020
Summary
Cassini
Area of Science:
- Planetary Science: Investigating the thermal properties and surface composition of Saturn's moon Tethys.
Background:
- A unique thermal anomaly, nicknamed "Pac-Man," was previously discovered on Tethys' leading hemisphere.
- This anomaly exhibits distinct day-night temperature variations and is linked to surface alteration by high-energy electrons.
- Previous studies correlated the anomaly with changes in visible color ratios, suggesting surface modification.
Purpose of the Study:
- To map diurnal temperature variations and analyze surface properties across Tethys' anti-Saturn hemisphere.
- To investigate the spatial variations in bolometric Bond albedo and thermal inertia, particularly within the "Pac-Man" region.
- To understand the influence of surface alteration mechanisms on Tethys' thermal behavior.
Main Methods:
- Utilized data from Cassini's Composite Infrared Spectrometer (CIRS) during daytime and nighttime observations of Tethys.
- Generated maps of bolometric Bond albedo and thermal inertia for Tethys' anti-Saturn hemisphere.
- Compared observed temperatures with thermal model fits to identify discrepancies and infer surface properties.
Main Results:
- Confirmed the presence of the "Pac-Man" thermal anomaly, showing negligible albedo variation but dramatic thermal inertia differences.
- Measured significantly higher thermal inertia (29±10 J m⁻² K⁻¹ s⁻¹/²) within the anomaly compared to surrounding areas (9±4 J m⁻² K⁻¹ s⁻¹/²).
- Identified smaller-scale variations in albedo and thermal inertia, potentially linked to competing surface modification processes.
Conclusions:
- The "Pac-Man" anomaly is characterized by distinct thermal inertia, suggesting significant surface alteration.
- Competing surface modification by E ring grains and high-energy electrons likely influence Tethys' thermal and albedo properties.
- Discrepancies in morning warming curves may indicate regional variations in surface roughness due to differing alteration mechanisms.
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