This is a Viking image of the surface of Mars. The footpad of the Viking lander is visible in the corner of the image.
Click on image for full size
When we ask "Where might we find extraterrestrial life", the first place many scientists turn to, because of its similarity to the Earth, is Mars. Mars is the closest analog to the Earth in both the present environment and its past. From experiments which were designed to identify life in the Martian soil at that time, the Viking mission to Mars returned a negative finding. Viking looked for life in only two sections of the entire surface of Mars. With the recent discovery of an asteroid from Mars which potentially contains the remains of bacterial life from Mars itself, it has been suggested that in the past, Mars may have harbored forms of life. Scientists are also more aware of the potential for life in extreme environments.
There is confusion about the potential for Mars to harbor life because it seems such a forbidding place for life as we know it; with a carbon dioxide atmosphere and little free oxygen. Yet there is evidence that Mars may have conditions remeniscent of Earth, with flowing water etc. Now a more detailed exploration of Mars, and the entire Mars environment is underway. Scientist want to understand more about the Martian climate and the potential for the climate of Mars to change over time and produce more oxygen in the atmosphere. Scientists also want to know exactly how much water is to be found on Mars, and in what form; ice or flowing water. Many scientists believe that if water can be found, even in reservoirs buried deep under the surface, then life may also be found there.
For a discussion of why other planets seem much less habitable than Mars for life as we know it, you may leave this tour and take the
Exploratour on Life in the Solar System.
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