Introduction: Circular and elliptical depressions, distinct from impact craters by their steep walls, lack of visible rims or ejecta, and flat floors, have been known to exist on Mars for over thirty years. Since their initial discovery in Chryse Planitia by [1], these features have been identified in Viking imagery at several locations, including Lunae Planum, Utopia Plani-tia, and Ares Valles...