DPS 2001 meeting, November 2001
Session 24. Io, Tori, and Satellite Atmospheres
Oral, Chairs: I. de Pater, W. Smythe, Wednesday, November 28, 2001, 5:00-6:40pm, Regency E

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[24.04] Thermal Output of Io from Galileo NIMS low and high spatial resolution measurements

W. D. Smythe, R. Lopes, L. W. Kamp, R. W. Carlson (JPL), Galileo NIMS Team

The thermal output of Io has been mapped by the Galileo Near Infrared Mapping Spectrometer from 1996 to present during 29 orbits of the spacecraft about Jupiter. The observations were made over the wavelength range 1-5 microns, measuring thermal output for surface temperatures ranging from about 200K to 1800K. The spatial resolutions range from about 600 kilometers to fractional kilometers. Measurements at high spatial resolution show many more hotspots than observed at lower spatial resolution. The low resolution observations permit assessing global and temporal variations in thermal output, while the high resolution observations provide details on regional activity at Pele, Loki, and Prometheus. The global output at 1-5 microns is consistent with astronomical observations. However, output from isolated small hotspots is not detected if the radiance per pixel lies beneath instrument sensitivity, which will result in slight underestimation of the global output. Thermal output is associated with low albedo features, though not all low albedo features have currently detectable thermal output. There is an apparent decrease in thermal output with increasing latitude in the present NIMS measurements, consistent with the distribution of small low albedo features. A few regions have exhibited significant changes in thermal output. Loki shows quasi-periodic variations with time and Pillan had a major thermal event in 1997. However, most of the thermal areas have produced essentially constant thermal output throughout the Galileo Mission.

This research was supported by NASA

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