The size and age of the universe are immense, and so, there is quite a reasonable chance of another planet like ours existing which can support intelligent life. It is because of this very reason that scientists today are persistently searching for signs of this very life rather than giving it up as a hopeless cause. However, many are also of the belief that sometimes, the signs lie closer than we think they are, and since our solar system could produce life on earth, there is every possibility that some other celestial body within the system has experienced similar circumstances, for even the sign of a basic unit of life as the simplest bacteria from the Monera family is a symbol of hope for life on that body in the future.
The main requirements of biological life on any celestial body are energy, air to breathe, and water – namely H2O, O2, and C (Carbon); our neighbor Mars, certainly satisfies quite a few of these criteria. There is a fact behind every myth, and the idea of the “little green alien” also has some scientific basis to it.
Climate and atmosphere wise, both Earth and Mars show several similarities like polar ice caps, weather patterns, and seasonal changes. This gives us an important idea of the atmospheric conditions of the planet, and their similarities to Earth’s atmosphere, and thus, indicating the probability of the presence of life on the red planet. The major difference between the atmospheres of the two planets is that the Martian atmosphere is around a 100 times thinner than that of Earth (it is assumed that because of Mars’ lower gravity, it couldn’t maintain a thick atmosphere), leading to lower and more extreme day and night temperatures than on the earth. The larger distance from the Sun also contributes to the lower temperatures, with the average temperature being -60 degree Celsius.
The atmosphere has a composition of 95% Carbon Dioxide, 2.7% nitrogen, 1.6% argon and 0.13% oxygen along with the presence of water in the form of clouds. The high carbon dioxide to oxygen ratio has lead to several scientists hypothesizing that Mars used to harbor life but is no longer able to – as respiration involves consumption of oxygen to release carbon dioxide. Another proof to support this theory is the fact that the atmosphere of Mars used to be thick enough for running water to exist on the surface. This evidence is seen in vast river plains and presumed ocean boundaries along with rocks affected by water.