THE CONTROL OF TARGET STRUCTURE ON THE CRATER MORPHOLOGY ON THE MOON, MARS, AND VENUS - EVIDENCE AND IMPLICATIONS. T. Öhman

The target topography and espe-cially layering within the target are widely known to cause deviations from the generalized crater-formation mechanisms [1 and references therein]. As a result, the crater morphology changes accordingly. Another, fairly unrecognized source of crater shape variation is the presence of faults, fractures or other similar planes of weakness in the target [e.g. 2, 3]. The resulting po-lygonal impact crater (PIC) shape can be used as an additional tool in deciphering the tectonic history of a cratered surface [e.g. 4]. Some observations of PICs, both from earlier stud-ies and our on-going research [e.g. 5–7], are not fully explained with the current ideas. Thus, new tentative hypotheses regarding the formation of PICs, as well as the effects of impact basin -induced modification on the surrounding crust are proposed.