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 specifically to observe locations where published accounts argue for the presence of landforms created by the interaction of a large body of water with Martian topography fail to reveal any evidence to support the hypothesis that the northern lowlands were once the site of oceans or seas. Given the difficulty of identifying ancient coastlines on Earth from orbital and aerial photography in the absence of field work, this result does not preclude the possibility that Mars once had large standing bodies of water on its surface, but calls into question shorelines previously proposed.