Scientists at NASA (the National Aeronautics and Space Administration) announced last week that they have found evidence of liquid water on Mars. The discovery has given scientists new hope that some form of life might exist on the planet.
Scientists believe that Mars once had rivers, lakes and oceans, but they thought that any remaining water was now frozen solid in polar ice caps.
Dr. Alfred McEwen studies photographs of the planet’s surface taken by a NASA spacecraft that orbits Mars. He and his team of researchers noticed that in some of the images there were dark streaks running down the sides of mountains and craters.
The streaks changed in size and colour depending on the time of year. They were longer and darker in the summer, and faded when the temperature cooled.
The scientists thought the streaks might be caused by water freezing and thawing as the seasons changed.
They used another instrument on the orbiting spacecraft to study the streaks. The instrument—called a spectrometer—can identify types of molecules based on which colours of light they absorb.
The spectrometer told them that the dark streaks were patches of soil containing hydrated salts—salt molecules that had soaked up water. Salt molecules would help keep water liquid at a lower temperature, in the same way salt helps to melt ice on sidewalks in the winter here on Earth.
Scientists believe water is necessary for living things, so they thought Mars was too cold and dry to support life. Now they think it’s possible that some form of microscopic life could exist in these damp patches of soil.
Finding these microorganisms could be difficult, however. The robotic devices that are currently being used to explore Mars are not allowed to go near the wet areas because scientists are afraid they might be carrying microbes from Earth. These microbes could contaminate any Martian life they might find.
Scientists are now looking at ways to sample the damp soil from a distance, possibly by using lasers. They are also considering sending up a spacecraft that has been sterilized to destroy any microbes from Earth.