Thursday, September 01, 2005

New Tethys Image: Tethys in the Dark

CICLOPS has released this processed view of Tethys taken on August 3, when Cassini was 842,000 km from the satellite. Only a thin crescent was visible of Tethys at the time this image was taken, when the phase angle was 144 degrees. Images like these can be used to study the photometric properties of the surface material on Tethys, particularly with how backward scattering it is. Two good sized craters can be seen along the terminator, or the dividing "line" between night and day. The one at about the 3:30 position is Penelope. The smaller crater near 5:30 is Antinous. While it hasn't been stretched to make it visible, much of the left part of Tethys' disk viewed here is lit dimly by Saturn-shine. This technique, however, requires longer exposure times than those used here to be useful for geologic analysis.

This image has a resolution of 5 km/pixel.