Water on Mars - page 2

Where Did the Liquid Water Go?

The question of what caused the demise of liquid water on the Martian surface is still a mystery. But many scientists believe the disappearance of water could have been the result of climate change over billions of years as Mars gradually lost its atmosphere.

Some of the water would certainly have been lost to space through evaporation, but there is almost certainly a substantial amount of water still trapped beneath the surface, as water ice and maybe liquid deep underground. Images obtained by the Mars Odyssey in 2002 show large amounts of subsurface water ice in the northern arctic plain. The Gamma Ray Spectrometer (GRS), a suite of instruments on the MGS, detected large amounts of water-equivalent hydrogen in the upper meter (3 feet) of soil in a region near the Martian south pole. When cosmic rays hit the Martian surface, gamma rays and neutrons scatter. By measuring the energy of the rays and neutrons, the GRS can determine what elements are present in the soil.

Instruments on the Gamma Ray Spectrometer detect neutrons that scatter when cosmic rays hit the Martian surface. By measuring these neutrons, it is possible to calculate the abundance of hydrogen on Mars, thus inferring the presence of water. (Image credit: NASA)

Based on the data from the GRS, researchers were able to create neutron maps of the Martian surface showing the locations of water-equivalent hydrogen-rich soils. From about 55 degrees latitude to the poles, the soil contains about 50% water by mass. This means that a kilogram/pound of soil from these regions would yield about half a kilogram/pound of water.

Deep underground, there may also be hidden reservoirs of liquid water that occasionally burst through to the surface in the form of brief flash floods. If you go deep enough below the Martian surface, temperatures and pressures become warm enough to support liquid water. And on Earth, there are many locations where liquid water and ice co-exist in below-freezing conditions. Lake Vostok, a subglacial lake in Antarctica, is one example.

Water can exist as a liquid even beneath ice. This photo shows a subglacial stream exiting the terminus of Harriman Glacier in Prince William Sound, Alaska. (Image credit: U.S. Geological Survey)
But, Mars is another planet and some scientists caution against allowing earthly biases to unduly influence the interpretation of features on Mars. Its geology and terrain have amazed us many times already, and it will no doubt surprise us again in the future. As the first space exploration mission to return data from a Martian polar region, Phoenix will provide an important contribution to NASA's overall Mars science strategy "Follow the Water".

What's in a Name?

History shows that naming a planetary feature after something we Earthlings are familiar with can sometimes have long-term, unintended consequences. In the late 1800s, Italian astronomer Giovanni Schiaparelli may have inadvertently sparked the belief in Martian canals when he named the linear features he saw on the Martian surface "canali" - which translates to channels or canals. Schiaparelli did not intend for this to be interpreted as "artificial" canals; he meant simply "narrow waterways." But the coined phrase took on a life of its own, and even provoked some ideas that Martian intelligent life had constructed a canal system to bring water from the polar regions to its cities.

Mars Face
In 2001, the Mars Orbiter Camera acquired a high-resolution image of the "face on Mars," showing that it was actually a highly eroded mesa that resembles a human face at certain times of the day when lighting casts shadows on the landform. (Image credit: NASA/JPL/Malin Space Science Systems)

A similar phenomenon happened in the 1970s when a landform that resembled a human face turned up in photos taken by the Viking Mission cameras. The "face" - which was actually a mesa - is located in the Cydonia region of Mars, an area whose geography is much like that of the Colorado Plateau in the southwestern United States. The image was taken at a time of day when shadows on the summit caused the mesa to have a face-like pattern, so scientists on the Viking team lightheartedly named the landform the "Face on Mars." A media frenzy ensued, and some face-believers were convinced that NASA was trying to cover up evidence of civilization on Mars. The furor became so intense that when the Mars Global Surveyor arrived at Mars in 1997, NASA instructed mission scientists to reprogram the spacecraft so that it could look in the direction of "the face" and take a high-resolution photograph. These images confirmed that the "Face on Mars" was indeed a highly eroded mesa that, at certain times of the day, looked like a face due to shadows created by gullies in the eroded rock.

One can only wonder what drama may lie ahead for the landforms at the Martian south pole named "swiss cheese terrain."

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