Strange Hillocks And Ridges On Mars
On the northwestern flanks of the huge Martian volcano Arsia Mons are countless hillocks of undetermined origin. Mostly 100 to 500 meters in diameter, the hillocks cover the edge of the volcano flank. In addition, the outer edge of the flank is surrounded by dozens of parallel ridges that stretch lengthwise for hundreds of kilometers, A peculiar feature of the ridges is that they have not been disturbed by craters or flow features; there are not even any variations in surface brightness. One explanation suggests that both hillocks and ridges were created in a huge landslide.
(Anonymous; "Strange Hillocks and Ridges on Mars," Science News, 113:43, 1978.)
Comment. The hillocks resemble the much smaller terrestrial Mima Mounds.
Reference. Martian topographical anomalies are cataloged in Section AME in The Moon and the Planets. Further information on this book is located here.