ABSTRACT
Infrared spectral images of Jupiter's volcanic moon Io, acquired during the October and November 1999 and February 2000 flybys of the Galileo spacecraft, were used to study the thermal structure and sulfur dioxide distribution of active volcanoes. Loki Patera, the solar system's most powerful known volcano, exhibits large expanses of dark, cooling lava on its caldera floor. Prometheus, the site of long-lived plume activity, has two major areas of thermal emission, which support ideas of plume migration. Sulfur dioxide deposits were mapped at local scales and show a more complex relationship to surface colors than previously thought, indicating the presence of other sulfur compounds.
Subject(s)
Jupiter , Spacecraft , Volcanic Eruptions , Extraterrestrial Environment , Hot Temperature , Spectroscopy, Near-Infrared/methods , Sunlight , TemperatureABSTRACT
The Near Infrared Mapping Spectrometer performed spectral studies of Jupiter and the Galilean satellites during the June 1996 perijove pass of the Galileo spacecraft. Spectra for a 5-micrometer hot spot on Jupiter are consistent with the absence of a significant water cloud above 8 bars and with a depletion of water compared to that predicted for solar composition, corroborating results from the Galileo probe. Great Red Spot (GRS) spectral images show that parts of this feature extend upward to 240 millibars, although considerable altitude-dependent structure is found within it. A ring of dense clouds surrounds the GRS and is lower than it by 3 to 7 kilometers. Spectra of Callisto and Ganymede reveal a feature at 4. 25 micrometers, attributed to the presence of hydrated minerals or possibly carbon dioxide on their surfaces. Spectra of Europa's high latitudes imply that fine-grained water frost overlies larger grains. Several active volcanic regions were found on Io, with temperatures of 420 to 620 kelvin and projected areas of 5 to 70 square kilometers.
