Did water used to flow on the surface of Mars? In order for life to exist on a planet, many scientists believe it is essential for the world to possess liquid water.Įver since technology has enabled mankind to gaze at Mars in detail, humans have been looking for indications that there was water on the red planet. However, the surface of the planet is so cold, this water exists only as ice. It is now widely believed that Mars holds a reasonably large volume of water. How important is the presence of liquid water? They found they are surprisingly thin – less than 10 feet (3 metres) and occur in topographical lows. The experts looked at what types of landforms the salt deposits formed on and how they were deposited across the terrain. To zoom in, scientists turn to the High-Resolution Imaging Science Experiment (HiRISE) color camera, allowing them to see details as small as a Mars rover from space. MRO has two cameras suited for this purpose – the Context Camera, with its black-and-white wide-angle lens, helps scientists map the extent of the chlorides. Using data from MRO, Leask and Ehlmann conducted a broad study of all of the known salt deposits. It has accumulated data on Mars over the last 15 years. MRO, meanwhile, launched in August 2005 and reached Mars in March 2006. Not only did they offer evidence that Mars had been much wetter long ago, they also offered a way to determine the last time that water had existed in liquid form on the planet's surface. Hundreds of deposits of sodium chloride stretching tens to hundreds of square kilometers in area were discovered by NASA's 2001 Mars Odyssey orbiter starting in 2008. Mars once rippled with rivers and ponds billions of years ago, providing a potential habitat for microbial life.īut as the planet's atmosphere thinned over time, that water evaporated, leaving the frozen desert world of the present day. 'As such, these deposits must have formed during the evaporation of the last large-scale water on the planet. 'Salt is incredibly soluble, so any moisture at all would dissolve it,' said Leask, now a postdoctoral scholar at Johns Hopkins University's Applied Physics Laboratory. By counting the number of craters on an area of the surface, scientists can estimate its age.Ĭhloride salt deposits on Mars are 'intriguing', the duo say, because they dissolve very readily and so record the last stage of liquid water present at Mars' surface. Generally, the fewer craters a terrain has, the younger it is. The scientists also found winding, dry channels nearby – former streams that once fed surface runoff (from the occasional melting of ice or permafrost) into these ponds.Ĭrater counting and evidence of salts on top of volcanic terrain allowed them to date the deposits. Using both cameras to create digital elevation maps, Leask and Ehlmann found that many of the salts were in depressions once home to shallow ponds on gently sloping volcanic plains. The team looked at imagery of deposits of sodium chloride (table salt) captured by the Mars Reconnaissance Orbiter (MRO). The new study was conducted by Ellen Leask and Bethany Ehlmann, two researchers working at Caltech's Division of Geological and Planetary Sciences.
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