Analyzing surface ruggedness inside and outside of ice stability zones at the lunar poles

Abstract

We measured surface ruggedness within 12 polar craters on the Moon, six at each pole, using a variation of the Vector Ruggedness Measure (VRM*). We compare VRM* values derived within ice stability zones, where maximum surface temperatures are ≤112 K, to VRM* values from warmer surfaces where ice is not stable. Ruggedness values inside and outside of ice stability zones are statistically not from the same continuous distribution (α = 0.05). In nine of the 12 investigated craters, surfaces where ice is stable are smoother than neighboring warmer surfaces. These comparatively smooth surfaces are observed in both craters that host surface water-ice exposures and those that do not, suggesting that the presence of subsurface ice, rather than surface ice, may be responsible for the reduced surface ruggedness derived from a moving window of 3 × 3 cells applied to 120 m elevation models. Reduced ruggedness of ice stability zones is slightly greater in south polar craters and tends to correlate with enhanced hydrogen content as modeled from Lunar Prospector data. While ice stability zones may have a control on the distribution of softened topography at the lunar poles, the magnitude of this softening is small at the investigated baselines.