If this is true, Mars must have had life at some point.

New study supports existence of Mars ocean shoreline

WASHINGTON – Long, undulating features on the northern plains of Mars probably are remnants of shorelines of an ocean that covered a third of the planet’s surface at least 2 billion years ago, scientists said today.

The geological features, stretching thousands of kilometres, were first revealed in the 1980s in Viking spacecraft images. But topographical data collected by Nasa’s Mars Global Surveyor in the 1990s cast doubt on whether the features truly marked a long-gone sea coast.

An illustration shows how Mars might have appeared more than 2 billion years ago, with an ocean filling the lowland basin. Photo / Reuters