Origin of circular collapsed landforms in the Chryse region of Mars

The quasi-circular collapsed landforms occurring in the Chryse region of Mars share similar morpholog- ical characteristics, such as depth of collapse and polygonally fractured floors. Here, we present a statis- tical analysis of diameter, maximum and minimum depth, and amount of collapse of these features. Based on their morphometric characteristics, we find that these landforms have a common origin. In par- ticular, the investigated landforms show diameter-depth correlations similar to those that impact craters of equivalent diameters exhibit. We also find that the observed amount of collapse of the collected fea- tures is strongly correlated to their diameter. Furthermore, the linear relation between minimum filling and pristine depth of craters, the constant ratio between collapse and the amount of filling and the frac- tured and chaotic aspect of the filling agree with melting and subsequent collapse of an ice layer below a sediment layer. This interpretation is consistent with a buried sub-ice lake scenario, which is a non-climatic mechanism for producing and storing abundant liquid water under martian conditions.