Mars, the rugged Red Planet, may have once been blue, according to new research that suggests massive ancient oceans that once covered a third of its surface. The new findings by a joint Canada-U.S. research team provide strong evidence that kilometre-high features seen on the planet’s surface today are actually the shorelines of ancient seas.
http://www.berkeley.edu/news/media/releases/2007/06/13_mars.shtml

J.T. Perron, J.X. Mitrovica, M. Manga, I. Matsuyama and M.A. Richards:“Evidence of an ancient martian ocean in the topography of deformed shorelines“