The long, straight structures visible on the surface of Mars are not fault lines caused by the movement of tectonic plates, but are in fact a series of long, low ridges and hills called dykes. Geophysicists have argued for years that Mt Olympus on Mars - the largest volcano in the solar system - could only have been so big if there were no tectonic plates on the planet. Now numerical simulations by Dan McKenzie and Francis Nimmo from Cambridge University in the UK suggest that if the structures are indeed dykes, then they may have provided a heat source that have melted ground water. Evidence surrounding the dykes suggest they have caused enormous floods in the past (Nature 397 231).
Mars is now a dry planet with most of its water either tied up in a deep permafrost or lost to outer space. However, images gathered by Mars Observer and earlier space craft such as the Viking orbiters, showed evidence of water channels, rivers, and water erosion. The most striking evidence consists of wide enormous flood plains in the Valles Marineris area.
Dykes are created when magma from deep inside the planet swells upwards and deforms the surface. The dykes on Mars are in the Tharis bulge, a region of the Martian surface that has a large volcanic plume underneath it. These dykes are 20 times bigger than anything seen on the Earth.
McKenzie and Nimmo calculated the amount of heat required to melt the Martian permafrost and modelled their results on a computer. They discovered the dykes produced enough heat to melt at least 7500 km3 of water – enough to have radically changed the surface temperature and humidity on the planet, and produced the water erosion seen in the region.
