The Image of Mt. Etna which caught a qualitative change of sulfur-dioxide gas by ASTER TIR data (Sulfur dioxide (SO2) has the absorption characteristic in thermal infrared region. 2000/5/7 day 2000/6/6 night 2000/10/28 night The Observed Image of Sulfur Dioxide (SO2) Emitted from Mt. Etna Volcano. (Red shows high concentration.) About the extraction image of high concentration sulfur dioxide (SO2) Color scale = E［T11］/Average（E［T10］and E［T12］ only the pixel of <0.494 is displayed. Background is the gray scale of the TIR band 14.