Data for this image was recorded by Magellan during the first cycle of Venus orbits in September 1990 using Magellan's synthetic aperture radar (SAR). North is towards the top of the image, and radar illumination is from the left at an incidence angle of 38 degrees. The image is centered at 20.2 degrees south latitude and 338.7 degrees east longitude, west of Alpha Regio in the Navka region of Venus, and covers a section of the surface approximately 150 kilometers (93 miles) in width by 200 kilometers (124 miles) in length. Two circular areas with low radar back scatter cross-sections can be seen in the image, and are most likely due to meteoroid-atmosphere interaction. Large, radar-dark regions like the ones in the image, often called "dark margins," have been observed in association with about half of the impact craters on Venus, and it is speculated that such regions are the product of atmospheric shock waves from impactors. A second hypothesis attributes the dark regions to fine deposits of material created on impact or by ablation during atmospheric transit. The dark margin in the southern half of the image appears to surround a small, irregular impact crater or multiple crater, though the feature to the north does not. This suggests that the latter was due to a smaller meteoroid, one destroyed during transit, but large enough to create a shock or pressure wave able to deform the surface. Both radar-dark areas are about 50 km (31 miles) in diameter.
