The near perfect circle and smooth contours suggests a direct hit by a comet traveling at such a high rate of speed it liquefied the ground and caused the “bouncing drop” effect one observes when a water drop falls in water...the final fall of the now partially cooled ball of Martian turf forming the cone while the still hot and gooey inner core collapses back into the depression to make the hole...
...just a guess-and if I am right the interior of the formation would resemble a domed stadium with a skylight--good location for shelter and terraforming.