The Radar Heterogeneity of Mars

Diffuse scattering from Mars is much more substantial than for the other quasispecular targets and often accounts for most of the echo power, so the average near-surface abundance of centimeter-to-meter-scale rocks presumably is much greater on Mars than on the Moon, Mercury, or Venus. Features in Mars SC spectra first revealed the existence of regions of extremely small-scale roughness (see 

FIGURE 15 Arecibo 13-cm delay-Doppler images of the (a) north and (b) south poles of Mercury, taken in the SC polarization. The resolution is 15 km. The radar-brightness regions are shown here as dark. [From Harmon, J. K., Slade, M. A., Velez, R. A., Crespo, A., Dryer, M. J., and Johnson, J. M. (1994). Nature 369, 213-215. Copyright 1994 Macmillan Magazines Limited.] 

FIGURE 16 Arecibo delay-Doppler OC radar map of Maxwell Montes on Venus. (Courtesy of D. B. Campbell.) 

Echoes from 37 main-belt asteroids (MBAs) and 58 near-Earth asteroids (NEAs) have provided a wealth of new information about these objects sizes, shapes, spin vectors, and surface characteristics such as decimeter-scale morphology, topographic relief, regolith porosity, and metal concentration. During the past decade, radar has been established as the most powerful Earth-based technique for determining the physical properties of asteroids that come close enough to yield strong echoes. 

The polarization signatures of some of the largest MBAs (e.g., 1 Ceres and 2 Pallas) reveal surfaces that are smoother than that of the Moon at decimeter scales but much rougher at some much larger scale. For example, for 

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