The fascination with finding water on Mars is continuing apace at a fair rate of knots. At www.dailygalaxy.com/my_weblog/2013/07/caltech-researchers-discover-evide… … Mike Lamb of Caltech and co-author of a paper published in the Journal of Geophysical Research thinks they have evidence that the northern lowlands of Mars is a dried up ocean sea bed (covering a third of the planet). They used high resolution images from the Mars Reconnaissance Orbiter to focus on a 100 square km area they thought might sit on the former coastline. They found inverted channels which form, it is thought, when large gravels and cobbles are carried along by rivers and deposited along the bottom, building up over time. Once the river has dried up the finer material, such as clays, silts and sands, erode away (so none of that fine material is visible in the images). What is there is the gravels and cobbles and they form ridge like features – which means it is not necessarily the right interpretation, but a good guess. These channels also appear to form a fan – which may indicate a former delta.