Friday, February 13, 2015

Water on Mars

Ever since Giacomo Miraldi observed white spots near the poles of Mars in 1704, scientists have been wondering whether Mars has water. Sir William Herschel, the British Astronomer Royal, assumed that the dark areas he observed through his telescope were oceans, but in the 20th century, the idea of currently having liquid water on the surface of Mars was rejected. In 1964, when scientists were able to send Mariner 4 into the universe, they received clear images of Mars. These images show that there were only ice caps at the north and south poles of the planet, with no evidence of water existing on the surface today.

There are two principal reasons why water is not found today on the surface of Mars. First of all, Mars is much farther away from Sun than the Earth is. According to NASA, the longer distance makes the average Martian temperature 130 degrees Fahrenheit less than that of Earth. In addition, the Earth’s atmospheric pressure is about 100 times that of Mars. Under such low pressure, water condenses into ice easily.

Water partially filling Gale Crater.
However, there is speculation that surface water may have existed at one time. In 2011, mineral-mapping data from more than 350 sites showed evidence of clay that would have formed billions of years ago. Since rocks have to interact with water to form clay, the appearance of clay on Mars suggests that water had existed, even though maybe only for a short period of time. More evidence for past water came in 2014, when NASA’s Curiosity rover found evidence of an ancient lake in Gale Crater. Scientists believe that a river once flowed into the crater, bringing bits of sediment and depositing them in the lake.
Mount Sharp
These sediments slowly formed into rocks. The river brought in enough water to help form Mount Sharp, an 18,000-foot-high mound of sediment at the center of Gale Crater. The discovery of clay suggests that Mars may have been once warm and wet, and thus may have been able to support life. Some scientists have even made the bolder claim that Mars once has a thicker atmosphere that raised the temperature above water’s freezing point, but this has yet to be proved. 

Two future NASA missions will look for further evidence of past water and life on Mars. In January 2016, NASA is going to launch the ExoMars Orbiter. It is designed to figure out if life ever existed on Mars. In 2020, NASA will launch a robotic science rover to further search for possible signs of past microbial life on Mars by studying the different kinds of soils and rocks. It will also address the challenges that human will face during future expeditions on Mars. Other tasks of this rover include testing the ability to extract oxygen from Mars’ atmosphere and monitoring its weather and dust storms.

- Jiaxuan Liu
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