M. Ramsey, Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, PA

J. Dehn, Geophysical Institute/Alaska Volcano Observatory, University of Alaska, Fairbanks, AK

Thermal infrared (TIR) surface observations of Earth and Mars have added to a wealth of information for volcanoes and their eruptive products. Much of this information comes from quantitative data extraction algorithms developed using Earth-based data as analogs. Effects such as compositional mixing, non-isothermal surfaces at the pixel scale, and surface coatings are all are being explored with terrestrial data to better understand similar information being returned from other planetary surfaces. One of the most difficult environments for which to examine many of these complications is that of active silicic volcanoes. Intermediate to silicic volcanoes with active lava domes commonly present an emitting target that is highly non-isothermal, typically obscured by some amount of volcanic plume, and can be areally mixed (i.e., fumarolic sublimates, vesiculated textures, petrologic variations). Although active silicic systems are not a factor on Mars, they provide an excellent algorithm development opportunity. One such example is the presence of non-isothermal elements on the surface. Integrated, these produce a non-linear composite of emitted energy that ultimately results in large errors where attempting to extract an accurate emissivity spectrum. This situation arises over active cold lava domes with a small areal abundance of very hot cracks, and on the surface of Mars, which commonly has a small fraction of warm rocks surrounded by colder dust.

Data returned from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of several volcanoes in the Kamachaka region of Russia have been examined. These data captured various states of eruption, flow deposition, and passive states. In addition, ground- and airborne-based FLIR images have been collected to provide a small-scale spatial context. It was found that thermal anomalies varied significantly over time on the active domes and clearly show the onset of new phases of activity as well as the semi-quiescent hydrothermal background. However, many of the aforementioned complications are also present. New models for accurate spectral retrievals have been developed, which further refine the extraction of accurate emissivity from temperature in TIR radiance data. Results have an impact on the spectral analysis of the reconstructed emissivity to better quantify the chemistry and texture of the erupted material. Such approaches could easily be adapted for TIR data acquired over volcanic units on other planetary surfaces.

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Submitted: American Geophysical Union Fall Meeting
Date: December 13 - 17, 2004