Vertical roughness of Mars from the Mars Orbiter Laser Altimeter

The vertical roughness of the martian surface at similar to 250 m spatial s cales has been determined in two global latitude bands: an equatorial and a high northern band acquired from 18 tracks of data by the Mars Orbiter Las er Altimeter (MOLA) during the Fall of 1997. The distribution of RMS vertic al roughness, as derived from MOLA pulse widths, for the equatorial band is non-gaussian, with an overall mean of 2.8 m RMS, but with secondary popula tions at 1.5 m and 2 - 6 m RMS. The higher latitude northern plains of Mars are almost uniformly similar to 1 m RMS in their vertical roughness charac teristics, suggesting that they are smoother than virtually any terrestrial deserts. We suggest that dust mantling has muted the local topography of M ars, rendering it as smooth as 1-2 m RMS. Heavily cratered uplands near the martian equator are noticeably rougher, indicating more rugged and less-ma ntled local topography.