Younger crater materials of c 4 age, intermediate plains material, and small patches of smooth plains material are superposed on all other units. Its extensive ejecta blanket and secondary crater field are superposed on plains materials and older craters. This unit covers vast expanses of Borealis Planitia, a depression about 1,000 km in diameter that has an irregular arcuate west boundary. All attributes created during the creation process were verified by displaying the lines in both the database and the spatial coverage, but no formal tests were performed.
Line geometry is topologically clean.
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