RADIALLY FRACTURED DOMES - A COMPARISON OF VENUS AND THE EARTH

Radially fractured domes axe large, tectonic and topographic features discovered on the surface of Venus by the Magellan spacecraft. They ax e thought to be due to uplift over mantle diapirism, and to date axe k nown to occur only on Venus. Since Venus and the Earth axe grossly sim ilar in size, composition and structure, we seek to understand why the se features have not been seen on the Earth. We model the uplift and f racturing over a mantle diapir as functions of lithospheric thickness and diapir size and depth. We find that lithospheres of the same thick ness on the Earth and Venus should respond similarly to the same sized diapir, and that radially fractured domes should form most readily in thin oceanic lithospheres on Earth if diapiric activity is similar on the two planets. However, our current knowledge of the Earth's oceani c floors is insufficient to confirm or deny the presence of radially f ractured domes. We compute the expected dimensions for these features on the Earth and suggest a search for them to determine whether mantle diapirism operates similarly on the Earth and Venus.