http://SaturnianCosmology.Org/ mirrored file For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== This Viking photomosaic shows flat, featureless martian topography near the Utopia impact basin. This shaded relief map generated from Mars Global Surveyor data shows the same topography as the adjacent Viking image but reveals many ridges not visible in the earlier image. *Mars' Missing Ocean: A New Look at the Northern Plains * *By <* Science Editor < <posted: 07:00 am ET 05 April 2001 < There may be , or may have been , water on Mars but a debate over apparent shorelines on the planet's vast northern plains continues, with new research suggesting the features have nothing to do with what others have interpreted as a one-time enormous ocean. The author of the new analysis of gentle, parallel ridges in the blandest, flattest northern plains of enigmatic Mars argues instead that the features are large landscape bumps that resulted simply to relieve surface pressure from massive volcanoes, such as Tharsis, and other structures on the planet's surface. "We don't see the paleo (ancient) shorelines that some people see," said Paul Withers of the Lunar and Planetary Laboratory at the University of Arizona. "We see an network of tectonic ridges that helps us explain how the Tharsis volcano formed. I wouldn't make too many sweeping conclusions about whether there was or was not an ocean based on this. The northern plains are still flat and nobody has a clue why." * Tectonic forces * Unlike plate tectonics, which collide, disrupt and mold huge land forms on Earth, the tectonic forces at Mars result from the stresses required to hold up mountains and volcanoes -- some of which reach as high as 10 miles (16 kilometers). Those stresses build up over time and cause crustal compression that eventually squeezes large slabs of land and forms the ridges that initially look like shorelines, Withers said. The features likely formed about 3 billion years ago. Withers and his colleague Gregory Neumann of the Massachusetts Institute of Technology and the NASA Goddard Space Flight Center in Maryland published their brief analysis in this week's issue of the journal /Nature/. * Raised lips * The tip-off to a non-oceanic origin for the ridges included raised lips adjacent to ridges on what is the most featureless landscape in the solar system, Withers said. Withers and Neumann analyzed topographic data on the ridges measured in the past few years by NASA's Mars Global Surveyor, currently orbiting the Red Planet. "Specifically what we saw on one group was a nice flat terrace you'd associate with a shorelines, and then a raised lip on what would be the ocean-ward side of this terrace," Withers said. "It's difficult to imagine how you'd form this by an ocean or sea washing in and then receding away to leave this lip." The new research, arguing against a 1999 paper published by Brown University's James Head and colleagues, relies on more data than the previous team had. Head's team argued for an ocean that covered the northern third of the planet -- adding to mounting evidence that Mars once harbored life. It was a finding compatible with others coming earlier and later, pointing to what looked like enormous dry river channels once flooded with water or carved by ice. Those channels feed into the northern flatlands basin. But the new data show a network of ridges crisscrossing the plains, as well as many smaller ridges there, Withers said -- features you wouldn't expect on an ocean floor. "All the attempts to find shorelines or not -- they don't seem to be succeeding too well," Withers said, referring to similar work by Mike Malin and colleagues, where they searched for evidence of shorelines and failed to find them. * Ocean still possible * Withers remained open to the idea that the flatlands once harbored an ocean, but said, thus far, the evidence is not apparent. "No one has a clear [idea] what a billion-year-old shoreline on Mars is going to look like, but it's unlikely to look like the candidates that we've tested," he said. "This featureless area on Mars is covered with this network of tectonic features will give geophysicists something to think about." James Head is thought to be working on a longer analysis of the ridge features that could be published later this year. He was out of the country Wednesday and could not be reached for comment. * The Earth model * Victor Baker, a planetary geologist at the University of Arizona who also has studied Mars' northern flatland ridges, was an early advocate of the northern ocean idea. Competing teams of researchers have been studying somewhat different sets of ridge features in this area on Mars, Baker said. "The ones that Head and others had interpreted had always been suspiciously possible tectonic forms because of their scale," he said, "so that's not an interpretation that would surprise me." And Withers' and Neumann's finding actually could still point to the idea of a northern ocean, Baker said. "It's not inconsistent with this having been a basin which could be a possible receptacle for water because obviously the Earth's ocean basins are tectonic features. Tectonic processes resulted in those depressions. So the fact that these are tectonic features that line up along the margins doesn't say anything about whether there was ponded water there." "It's very difficult to prove the positive and it's difficult to say there never was any water there. We have a lot of other indications that inundation of the northern plains to some degree or other, by some processes related to water, possibly mud flows, has occurred during martian history. But it's difficult to establish that in an absolute way that will get the whole community to believe it."