  Surface roughness is an important metric in understanding how the geologic
history of an asteroid affects its small-scale topography and it provides an
additional means to quantitatively compare one asteroid with another. In this
study, we report the first detailed global surface roughness maps of 25143
Itokawa at horizontal scales from 8--32~m. Comparison of the spatial
distribution of the surface roughness of Itokawa with 433 Eros, the other
asteroid for which this kind of analysis has been possible, indicates that the
two asteroids are dominated by different geologic processes. On Itokawa, the
surface roughness reflects the results of down-slope activity that moves fine
grained material into geopotential lows and leaves large blocks in geopotential
highs. On 433 Eros, the surface roughness is controlled by geologically-recent
large impact craters. In addition, large longitudinal spatial variations of
surface roughness could impact the role of YORP on Itokawa.
