Liquid Water on Mars (Mars Society’s Red Planet Pen Blog)

By Nicole Willett (Mars Society Education Director)

Red Planet Pen Blog (Issue #39)


Scientists have carefully studied and tracked the history of water on the Red Planet.  It is now widely accepted due to the geomorphological evidence that Mars had an ocean of liquid water billions of years ago.  This ocean covered the northern hemisphere. This is indicated by the lower altitude of the surface, smoother and geologically newer surface of the northern hemisphere, as opposed to the higher altitude and the more jagged appearance of the highlands of the southern hemisphere.  An ocean covering most of the northern hemisphere has consequences such as a thicker atmosphere and warmer temperatures.

It is clear by photographic evidence that volcanic activity was very active in Martian history. In close proximity to ancient volcanoes are areas of catastrophic flooding, caused when volcanic heat rapidly melted the subsurface ice.  This evidence can still be seen today. (Nature6) Mars has a significant CO2 atmosphere, which would have been important to sustaining a warmer and wetter planet in the past.  This thicker atmosphere could have been in place for 10 million to a billion years. Volcanism and cycling of carbonate rocks would have helped to keep the atmosphere intact for this lengthy geologic time.  (Icarus)

Current science indicates Mars was once a warm and wet planet and currently has liquid water on the surface for short periods of time.  Data consistent with liquid water has been observed. It is proposed water appears seasonally as minerals are mixed with water that erupts through the surface and runs down the sides of craters, keeping it liquid at temperatures below freezing.  There is ample evidence, morphologically and spectroscopically, from the fleet of spacecraft that have been and are now presently working on and around Mars.


Water on Mars makes headlines often and has been debated for over a century.   Astronomer Giovanni Schiaparelli’s observations in approximately 1877 started the frenzy over water on Mars.  When Schiaparelli observed what he thought were channels on Mars, he called them canali which means channels. (See Figure 1)  When his findings were published, the term was misinterpreted as canals which led many people to believe intelligent life existed on Mars.  Channels and canals are distinctly different. A channel is a naturally occurring groove in the ground where water or some other fluid has eroded the soil away to make a riverbed.  A canal is made by sentient beings, for water to flow through. (Chaisson & McMillan) Schiaparelli declared his disbelief for water on Mars in a letter to Professor Holden in April 1893, in which he rejected the idea of water on Mars.  This was based on his study of the planet and the colors he observed. He states that when you view water on Earth from a higher point, it appears black which he did not observe. (Pacific)(Willett)

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