Water on Mars
Searching for the Missing Link
For a number of years now, missions to Mars have had a common goal: the discovery of water on the planet. From Viking, to Pathfinder, to Phoenix, missions to the Red Planet have advanced research and found new clues pointing to the presence of water on Mars. Thanks to our robotic explorers, scientists are fairly certain that there has been—and may still be—water on Mars.
Why is it important to find water on Mars?
A number of geological hints suggest that a great volume of water did exist on Mars some two billion years ago. If this is true, where did all the water go?, If we were to discover water, we might be able to determine how the Red Planet has evolved over the last few geological epochs. Also, the search for water is linked to the search for life. Finding water could be an indication that the Martian environment could be hospitable to life.
From theory to reality
It is impossible for liquid water to exist on Mars's surface as the atmospheric pressure and temperature are simply too low to sustain it. However, water molecules (H2O) are present on Mars in the gaseous (as water vapour) or solid state (as ice). When it snows on Mars, the snowflakes quickly change to water vapour, or sublimate, without ever passing through the liquid state.
So why do scientists believe that liquid water once existed on Mars? By comparing the Red Planet's geological footprint to Earth's, scientists maintain that the channels, valleys and ravines of Mars were formed in the presence of water. In other words, they appear to show that water once flowed over the surface of Mars. The discovery by Opportunity, one of the Mars Exploration Rovers, of the so-called "blueberries" (tiny spherules that react in the presence of water and are made of hematite and goethite), also strengthens the scientific evidence for the presence of water on Mars.
The Mars Global Surveyor (MGS) expedition was one of the turning points in the search for water on Mars. Images gathered by MGS, a satellite orbiting the planet, alerted scientists to the presence of a network of gullies and canals which, they suspect, are the result of surface and underground runoff. A comparative study of MGS images over the years has also shown the presence of sediment that could have been deposited by running water. Many scientists reject the possibility that this is windblown dust because, they claim, such deposits would not look like salt, as this sediment does.
Scientists are able to observe changes in the Martian surface thanks to the Mars Global Surveyor. The accumulation of white matter, which is identified as a sedimentary deposit by scientists, can be seen here. The sedimentary deposit would have been carried by a brief eruption of water. (Credit: NASA/JPL/MSSS)
In 2001, Mars Odyssey entered the annals of Martian exploration by discovering a large reservoir of water ice just south of Mars's north polar ice cap. That discovery was decisive in the choice of the landing site for the Phoenix mission, which landed in the Martian Arctic in order to probe the ice cap and determine its composition and properties.
More recently, the Phoenix Mars Lander mission enabled scientists to observe the behaviour of ice in the Martian Arctic. Though unsure at first about what they had found, mission scientists quickly came to the conclusion that the white substance discovered beneath the surface of Mars was indeed ice. Because it gradually disappeared once exposed to the ambient air, they concluded that it could only be water ice, since the temperature was too high for it to be dry ice (carbon dioxide ice).
The latest discoveries lead scientists to believe there could be water buried beneath the permafrost of Mars, and that it might, on rare occasions, well up. Meanwhile, missions are continuing, in the hopes that one day, the mystery of water on Mars will be solved.
This map shows the concentration of hydrogen in the Martian North Pole, which is believed to indicate regions rich in water ice. Areas with high ice content are shown in violet and those low in ice content are shown in red. The measurement of the concentration of water ice is based on gamma rays emissions from the hydrogen in the water.
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