PHOTOMETRIC PROPERTIES OF TRITON HAZES

Voyager imaging observations of Triton have been used to investigate t he characteristics of the atmospheric hazes on Triton at three wavelen gths: violet (0.41 mum), blue (0.48 mum), and green (0.56 mum). The gl obally averaged optical depth is wavelength dependent, varying from 0. 034 in green to 0.063 in violet. These photometric results are dominat ed by the properties of localized discrete clouds rather than by those of the thinner, more widespread haze known to occur on Triton. The cl oud particles are bright, with single-scattering albedos near unity at all three wavelengths, suggestive of a transparent icy condensate. Th e asymmetry parameter ( + 0. 6) and the wavelength dependence of the o ptical depth both indicate cloud particles 0.2-0.4 mum in radius. The clouds are concentrated at 50-60-degrees-S latitude, where opacities u p to three times the global average are observed. This is the same lat itude region where most of the evidence for current surface activity i s found, suggesting that the clouds may be related to the plumes or at least to some process connected with the sublimation of the south pol ar cap. The effects of possible temporal variations in the haze opacit y are examined. Increases in the haze opacity tend to redden Triton. H owever, the degree of reddening is not sufficient to explain the full range of observed changes in Triton over the past decade; variations i n the surface properties appear to be necessary. (C) 1994 Academic Pre ss, Inc.