A study of candidate marine target impact craters in Arabia Terra, Mars
Previous workers have proposed that a northern ocean existed early during
Martian geologic history and the shorelines of that ocean would coincide roughly with the
crustal dichotomy that divides the smooth, northern lowlands with the cratered, southern
highlands. Arabia Terra is a region on Mars that straddles the crustal dichotomy, and
several proposed shorelines are located in the area. Shallow marine impact craters on Mars
likely would exhibit features like those on Earth, including characteristic morphological
features that are distinctly different from that of craters formed on land. Common
attributes of terrestrial marine impact craters include features of wet mass movement such
as gravity slumps and debris flows; radial gullies leading into the crater depression; resurge
deposits and blocks of dislocated materials; crater rim collapse or breaching of the crater
wall; a central peak terrace or peak ring terrace; and subdued topography (an indicator of
both age and possible flood inundation immediately following impact). In this article, these
features have been used to evaluate craters on Mars as to a possible marine origin. This
study used a simple quantification system to approximately judge and rank shallow marine
impact crater candidates based on features observed in terrestrial analogs. Based on the
quantification system, 77 potential shallow marine impact craters were found within an area
bounded by 20 N and 40 N as well as 20 W and 20 E. Nine exemplary candidates were
ranked with total scores of 70% or more. In a second, smaller study area, impact craters of
approximately similar size and age were evaluated as a comparison and average total scores
are 35%, indicating that there is some morphological difference between craters inside and
outside the proposed shorelines. Results of this type of study are useful in helping to
develop a general means of classification and characterization of potential marine craters.