In 1877, the Italian astronomer Giovanni Schiaparelli observed Mars through a telescope and made a map of its surface. What he saw were lines crisscrossing the planet. He referred to them as "canali" which was translated as "canal" instead of "channel". In the early 1900's some people imagined intelligent life forms digging canals on Mars to bring water to populations which needed it. Such an explanation is called a hypothesis. A hypothesis is a scientific guess based on observations. Scientists verify hypotheses using further observations and experimentation.

Method: To get a closer look at the surface of Mars, the United States government agency NASA (the National Aeronautics and Space Administration) sent several Mariner probes in the 1960s and 1970s.

The spacecraft orbited the planet closely to take pictures. In 1975, two spacecraft were sent to land on the surface of Mars: Viking I and Viking II. They not only took pictures, but observed the soil. 

Robot arms performed several experiments to determine if the soil contained living organisms. In the summer of 1997, the Pathfinder mission continued observations and experiments with a vehicle that could move along the surface to explore a large area.

Results: The Mariner and Viking photos revealed that Mars has structures on its surface which are identical to dry river beds on Earth. These photos did not show signs of vegetation, canals, footprints or other signs of life. The Viking landers found no insects or other organisms in the soil.

The results of the experiments to find microscopic life were mixed. Most experiments had negative results but some had positive results. Unfortunately, the positive results could be explained by chemical reactions in the soil, not biological reactions. In terms of atmospheric conditions, the planet Mars is very cold (-23°C) and the atmosphere is almost entirely C0₂. The Pathfinder mission has not found life on Mars' surface yet, but may reveal some surprises in the years to come.

Conclusion: Mars does not have life on its surface. The dry river beds give the impression that there was liquid water there in the past. Since water supports life, living organisms may have evolved on Mars millions of years ago. The only water on Mars now is frozen at its north and south poles.

Future experiments: Although there is little evidence that life could exist on the surface of Mars, some scientists have formulated a hypothesis which supposes that life could exist under the surface, deep below the dry river beds.
NASA claims to have found traces of microscopic organisms that lived on Mars millions of years ago, but many scientists question the authenticity of the discovery. Future experiments will prove or disprove whether what NASA found was formed by extraterrestrial life or not.

The Greenhouse effect

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© Paul Billiet, Shirley Burchill, Alan Damon and Deborah James 2008