Triton's surface roughness is not unusual

Previous estimates of Triton's macroscopic roughness have been hampered by the presence of atmospheric aerosols in Triton's atmosphere: only a loose c onstraint on the macroscopic roughness (<20 degrees) could be obtained. Thi s study determines the locations of the clouds on Triton and then examines those areas found to be relatively devoid of cloud cover to yield tighter c onstraints on the surface macroscopic roughness. The most prominent cloud f eature is seen near 50 degrees S, 160 degrees W with smaller features appea ring near 60 degrees S, 270 degrees W and 15 degrees S, 280 degrees W. The fact that the cloud cover is not largest toward the south pole argues again st a sublimation origin for the clouds, though the results are not conclusi ve. The surface roughness ranges from similar to 11 degrees to similar to 1 8 degrees for Triton's various terrains. These are near the upper limit pre viously determined and, while relatively smooth, are not atypical of icy sa tellites. Roughness values near zero which would have been suggestive of an unusual surface texture and processes are clearly excluded. These results suggest that Triton's surface structure and the processes which govern its evolution are similar to those present on other icy satellites. (C) 1999 Ac ademic Press.