关于这张图
Sometimes we see circles on the Martian landscape with no apparent cause, such as in this picture of Utopia Planitia. Landscapes have rich histories, and what's happening here is likely the result of a long sequence of events. Impact craters are common throughout Mars' history. This area of Utopia Planitia has been buried by material and some of these craters have been buried with it. Loose material compacts over time and if there was the same thickness of material everywhere, then the surface would drop in height by the same amount everywhere. However, there's more of this material inside t…
