Well it has finally happened. After years of searching space for possible earth-like planets, a couple have been found. The tool used to find these new planets was the Kepler Space Telescope. What this indicates is that earth-like conditions are possible on other planets, however, size alone does not indicate the possibility of life.
In addition to having the right size for supporting life on an alien planet, the right chemical properties are also necessary. For example, on earth we know that life needs oxygen and water, therefore, we assume that life on other planets will also need these chemical components. However, recent findings on the planet earth also found life being supported on other chemical foundations. Extremophiles found in the darkness of deep oceans, are living off of silicates and other chemical bases.
Temperature also plays an important role in the likelihood that life exists on other planets. The "Goldilocks Zone" is a term that is used to describe the temperature range that can support life. The temperature cannot be too cold or too hot. It has to be "just right." To ensure the right mixture of hot and cold, the planet has to orbit so that its entire surface is exposed to periods of star thermal energy and deep space coolness. It also means that the planet cannot be too close or too far away from the star that it orbits.
With all of these requirements it is easy to see why so many scientists do not think that life on other planets is probable. However, if life can survive in non-earth-like conditions then the probability of life increases. For this year's astronomy science fair project, think about what life would be like if it evolved in an environment unlike what is found on earth. What physical adaptations would be necessary?