The following document lists the file abstract/BSCHMITT_IO_566.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
During the last 15 years, numerous studies have been devoted to the determination of the surface composition and temperature of Io, and their variation with longitude. In the near infrared (2-5 microns) SO2 frost is firmly identified, but the identifications of H2S and H2O are only tentative. In the mid-infrared S8, SO3, Na2SO3, NaHSO4 and Na2SO4 are tentatively identified with features seen in the Voyager IRIS spectra. Sulfur allotropes, alkali sulfides, and polysulfur oxides have also been proposed to explain the UV and visible spectra of Io. A clear identification of several of these molecules can be achieved with IR observations covering simultaneously a wide spectral range. Concerning the SO2 frost coverage, the current studies do not agree on the fractional area covered by SO2 and on the amplitude of their variations with Io's longitude. Regarding temperature, a better knowledge of the spatial distribution of the different types of regions of Io (ranging from large cold (100-130 K) regions to small hot spots (300-650 K)) are necessary for the study of the Io volcanism and of the surface-atmosphere exchanges. The goals of this observing program are (1) the positive identification of new molecules with simultaneous observation of absorption and emission features, (2) the determination of their abundances and their longitudinal variations, (3) the study of the surface and subsurface temperatures of the large and cold regions covered by SO2, and (4) the determination of the temperature and of the heat flow radiated from thermal anomalies. These issues can be addressed by ISO by (i) performing one high resolution spectroscopic observation in the near infrared (2.4-4.55 microns), (ii) measuring the whole mid-infrared spectrum (2.4-45 microns) at degraded spectral resolution, and (iii) repeating the mid-infrared spectral observation to study variations with Io's longitude. The very large spectral coverage of ISO is a necessary requirement to achieve all these scientific goals.