Why shouldn't the sky on Mars be blue? We don't really know what color it is, no "color" images are taken. The images we see are composites of
images taken with different filters. When these are combined the color results vary.
There are lots of right angles and straight lines in nature. Here are some right here on
Earth.
There is lots of sedimentary rock on Mars. When sedimentary rock erodes, it creates tiers. Here are some natural (and not so natural) tiers.