Oceans or seas in the Martian northern lowlands: High resolution imaging tests of proposed coastlines

Mars Global Surveyor Mars Orbiter Camera images that were targeted specific ally to observe locations where published accounts argue for the presence o f landforms created by the interaction of a large body of water with Martia n topography fail to reveal any evidence to support the hypothesis that the northern lowlands were once the site of oceans or seas. Given the difficul ty of identifying ancient coastlines on Earth from orbital and aerial photo graphy in the absence of field work, this result does not preclude the poss ibility that Mars once had large standing bodies of water on its surface, b ut calls into question shorelines previously proposed.