Ice suggests a sea was once on Mars

That water flowed on Mars in the past is well known. The planet's landscape includes giant canyons and dry river valleys. The NASA Mars rovers have found geological evidence for bountiful water early in Mars' history, billions of years ago.The Mars Express images, however, are the first to offer clues that Mars has had large bodies of water in the geologically recent past. The scientists said the sea, which would have frozen quickly, was about the size of the North Sea and at least 150 feet deep.