FRACTAL PROPERTIES OF CRATER EJECTA OUTLINES ON VENUS

Fractal property or self-similarity exists abundantly in many aspects in our universe. Fractals are rich in geology and have certain relatio ns to various geological processes. This article presents analyses of fractal properties of 18 impact crater ejecta margins on the surface o f Venus. The structured walk method was used to measure the length of perimeter of the ejecta margin and the resulting Richardson plots were investigated. Every R-plot has a first linear parr, a second part and a main scattering part. The variations seen in the second part includ e information on the formation and geology of the crater ejectas. The fractal dimension of the second part is related to the perimeter of th e ejecta and thus to the impact energy. The ratio of the square of the perimeter to the area describes the lobateness of the ejecta and has a positive correlation to the perimeter in a way similar to that betwe en the fractal dimension of the second part and the perimeter. Two lin ear subparts in the second part indicate different fractal properties due to various processes dominating on different scales. Scattering in the middle of the second part indicates the scale and type of the eje cta lobes. The smooth scattering over the entire second part is relate d to impact angle and energy. A threshold value beyond which the struc tured walk method cannot be used was observed at a ruler length of abo ut 1/10 of the perimeter.