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A high-amplitude thermal inertia anomaly of probable magnetospheric origin on Saturn’s moon Mimas |
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| Authors: | CJA Howett JR Spencer RE Johnson TA Hurford M Segura |
| Institution: | a Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80304, USA b Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston, TX 220758, USA c University of Virginia, Charlottesville, VA 22904, USA d John Hopkins University, 11100 John Hopkins Road, Laurel, MD 20723, USA e Goddard Space Flight Center, Mail Code 693, Greenbelt, MD 20771, USA |
| Abstract: | Spectral maps of Mimas’ daytime thermal emission show a previously unobserved thermal anomaly on Mimas’ surface. A sharp V-shaped boundary, centered at 0°N and 180°W, separates relatively warm daytime temperatures from a cooler anomalous region occupying low- to mid-latitudes on the leading hemisphere. Subsequent observations show the anomalous region is also warmer than its surroundings at night, indicating high thermal inertia. Thermal inertia in the anomalous region is  , compared to < outside the anomaly. Bolometric Bond albedos are similar between the two regions, in the range 0.49-0.70. The mapped portion of the thermally anomalous region coincides in shape and location to a region of high-energy electron deposition from Saturn’s magnetosphere, which also has unusually high near-UV reflectance. It is therefore likely that high-energy electrons, which penetrate Mimas’ surface to the centimeter depths probed by diurnal temperature variations, also alter the surface texture, dramatically increasing its thermal inertia. |
| Keywords: | Satellites Surfaces Satellites Composition Magnetospheres |
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