Large Quasi-Circular Features Beneath Frost on Triton
PAUL HELFENSTEIN 1,
JOSEPH VEVERKA 1,
DEREK MCCARTHY 1,
PASCAL LEE 1, and
JOHN HILLIER 1
1 Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853
Specially processed Voyager 2 images of Neptune's largest moon, Triton, reveal three large quasi-circular features ranging in diameter from 280 to 935 kilometers within Triton's equatorial region. The largest of these features contains a central, irregularly shaped area of comparatively low albedo about 380 kilometers in diameter, surrounded by crudely concentric annuli of higher albedo materials. None of the features exhibit significant topographic expression, and all appear to be primarily albedo markings. The features are located within a broad equatorial band of anomalously transparent frost that renders them nearly invisible at the large phase angles (
> 90°) at which Voyager obtained its highest resolution coverage of Triton. The features can be discerned at smaller phase angles ( = 66°) at which the frost only partially masks underlying albedo contrasts. The origin of the features is uncertain but may have involved regional cryovolcanic activity.
Submitted on June 10, 1991
Accepted on November 19, 1991
