Earth’s atmosphere is a mixture of nitrogen (79%), oxygen (20%), and a small fraction of carbon dioxide, water vapours and other gases. This makes the existence of life possible on Earth. However, the atmospheres on Venus and Mars mainly consist of carbon dioxide. The amount of carbon dioxide on these planets can range from 95% to 97%. This may be the reason no life exists on these planets.
The atmosphere of Venus is about 96 per cent carbon dioxide, with surface temperatures around 737 K (464 °C, or 867 °F). Venus itself rotates only once every 243 Earth days. Mars, in contrast, has a thin atmosphere composed of about 95 per cent carbon dioxide, with the remainder being mostly diatomic nitrogen.
