The red cells that caused the coloration of the red rain of Kerala gained scientific significance due to their possible extraterrestrial origin. A competing theory is that the red cells are spores of the Trentepohlia-genus that originated locally was lifted to the clouds and came down in rain. Hence a comparative study is required to decide whether the red rain cells are different from or indeed the same as Trenetepohlia spores. A comparative study was made of red rain cells and two species of Trentepohlia genus, namely Trentepohlia aurea and Trentepohlia umbrina. Red rain cells and Trentepohlia spores were differentiated on the basis of its morphology, absorption in the uv- vis regions, presence of DNA, ultrastructure, stability with regard to temperature, percentage of nitrogen and phosphorous in the cells and survivability in water. Our study showed that the red rain cells cannot be equated with Trentepohlia and still remain identified and distinct from known microbe on the earth
