Has Mars Always Been A Dry World? SpaceDaily

There may have been far less water on Mars in the past than most observers have assumed to date. The supposed ancient river channels may have been formed by katabatic winds carrying sand and dust over aeons, enhanced by flows of even purer carbon dioxide gas released when the dry ice permafrost warms up each year or occasionally when meteorites strike. If so, liquid water may never have been present on Mars, and the planet may always have been lifeless.