Kiel 2004 – wissenschaftliches Programm

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EP: Extraterrestrische Physik

EP 5: Mars, Staub

EP 5.5: Fachvortrag

Mittwoch, 10. März 2004, 17:05–17:25, C

Giant Polygonal Terrain: Relic of a Martian Ocean? — •Stephanie Werner, Stephan van Gasselt, and Gerhard Neukum — Freie Universitaet Berlin; Institute for Geosciences; Remote Sensing of the Earth and Planets; Malteserstr. 74 - 100, Haus D; D - 12249 Berlin

Utopia and Acidalia Planitae are occupied by extensive areas of polygon–forming troughs. This pattern is accompanied by ring–like structures interpreted as ghost craters. Their origin might be due to the shrinkage of desiccating sediments accompanied by differential compaction over buried topography. The material may be of sedimentary origin deposited in a standing body of water. We performed new measurements of crater size–frequency distributions (SFD) in Utopia and Acidalia in in areas of polygonal terrain and in surrounding units. All SFDs indicate for the smaller crater diameter size range an age of 3.4 Ga. We observe a deviation from the expected crater production function for the larger craters (D >3 km). For the polygonal terrain a combination of the clearly visible crater population and the ghost crater population yields an age of 3.8 Ga. Whatever obscures the expected production function of the crater SFD in the larger size range occurred between 3.4 and 3.8 Ga, and can be explained by extensive resurfacing events within a time span of roughly half a billion years. This is consistent with the existence of a proposed ocean in the northern lowlands.