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These images illustrate the three surface properties that affect a SAR image. For this slide and all the other SAR images in the slide set, the Magellan spacecraft was traveling north to south and looking to the left (east). All images in the slide set are displayed with north at the top of the image. In the left panel, lava channels on the southern slopes of Ovda Regio show the effects of topographic slope. Slopes facing away from the spacecraft (to the east) are elongated and appear to be in shadow, while west-facing slopes are foreshortened and radar-bright. The center panel shows Aurelia Crater. The brightness of the crater's ejecta and floor deposits indicates a surface that is very rough at the centimeter-scale-operating wavelengths of the SAR. Facets in the rough surface act as point diffractors and reflect back a lot of energy regardless of the incidence angle. In the right panel, notice that while the landforms do not appear to change much across the image, the western half of the image appears brighter. The western portion of the image is the southeastern portion of Maxwell Montes: At elevations greater than about 4 kilometers above mean planetary radius, the mountains are inherently more reflective, much like aluminum foil is more reflective than paper. High reflectivity at high elevations is nearly universal on Venus and is thought to represent differences in chemical weathering of rocks at high and low elevations. The left and center images are 90 × 180 kilometers, and the right image is 240 × 480 kilometers. Click here to view a high-resolution version of the image (0.99 MB)
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