Relating target properties to the planimetric shape of simple impact craters

Our aim in this study is to illuminate the dependence of planimetric crater shape on the properties of geological targets, as well as modification state. We have measured the rim trace of 110 comparatively fresh impact craters in HiRISE images (i.e., craters with preserved ejecta), as well as 840 fresh craters in MOC images. From the planimetric shape (i.e., the rim trace) we compute a suite of morphometric quantities, including Fourier harmonic amplitudes and measures of the deviation from radial symmetry. We compare the distributions of these quantities for craters that formed in targets exhibiting a range of properties, noting all statistically meaningful differences. We have also measured the departure from radial symmetry of the planimetric shape as a function of crater diameter, in which a clear transition is noted between D = 150 and 250 m. Moreover, globally-distributed craters exhibit a strong lateral elongation bias that may reflect an independent measure of Mars’ past obliquity variations.