Planetary scientists have uncovered telltale signs of water on Mars - frozen and liquid - in the earliest period of the Red Planets history. A new claim, made public this month, is that a deep ocean covered some of the northern latitudes.But the evidence for water grows much more scant after the Noachian era, which ended 3.5 billion years ago. Now Brown University planetary geologists have documented running water that sprang from glaciers throughout the Martian middle latitudes as recently as the Amazonian epoch, several hundred million years ago. These glaciofluvial valleys were, in essence, tributaries of water created when enough sunlight reached the glaciers to melt a thin layer on the surface. This, the Brown researchers write, led to "limited surface melting" that formed channels that ran for several kilometres and could be more than 150 feet wide.
Planetary geologists in the United States have analysed data that suggest Mars was once home to a huge ocean of water, covering nearly one-third of its surface. Their evidence, a ring of dry river deltas and valleys all at a similar elevation, adds weight to the idea that the red planet once supported an Earth-like water cycle.Hints that an ocean once occupied the northern lowlands of ancient Mars first arose in the late 1980s. Scientists examining pictures of the surface claimed to recognize extensive shorelines and vast networks of river valleys and outflow channels feeding in the same direction. Other researchers used thermal physics to imply that such networks could only have been carved by a complete water cycle, fuelled by one or more huge bodies of water.
The Red Planet harbours rocks rich in carbonate minerals, suggesting there was more water there in the past than previously thought, say scientists.Nasa's Mars Exploration Rover Spirit detected the carbonate-rich rocks in the Columbia Hills of Gusev Crater.This was in 2005, but Martian dust had partially blinded one of the rover's instruments, clouding the data.The team described in Science journal how they calibrated the instrument to "remove the effects of the dust". Nasa scientist Richard Morris, from the Johnson Space Centre in Houston, led the research. He said that the rocks, which are about 25% carbonate by weight, contain about 10 times more carbonate than had previously been detected in the planet's rocks.
Martian water most likely flowed as slurries of mud rather than trickling streams, according to a recent NASA report.The report, which compared signs of recent water activity in gullies on Mars with similar deposits on Earth, has implications for searching for evidence of water on the red planet. It could also indicate whether Mars has had liquid water within the last decade.